If you are interested in providing a fabric script for this please email me.


  1. Debian Anti-Spam Anti-Virus Gateway Email Server
    1. Features
    2. Debian Instalation
    3. Partition the Hard Drive:
    4. PuTTY and additional programs:
    5. The 2 minute vi tutorial:
    6. Verify System Settings
        1. resolv.conf
        2. hosts file
        3. mailname
    7. Apt-get Settings
      1. preferences
    8. Navigating the system:
    9. Firewall Rules
    10. Disable Unnecessary Daemons
    11. Configure NTP
  2. Installing Programs
    1. Installing Amavisd-new
    2. Postfix Configuration Part 1
      1. master.cf
      2. main.cf
        1. aliases www to postmaster
        2. myorgin domain and network
        3. message size
        4. local transport disable/error message
        5. virtual alias/ virtual email
        6. relay emails through outside
        7. reject nonexistent users
        8. where to forward valid mail
        9. relay domain only for example.com
        10. recipient delimiter
    3. Postfix Anti-Spam settings
        1. smtpd hello required
      1. restriction stages
        1. sender restrictions
        2. recipient restrictions
        3. smtp data restrictions optional
      2. content filtering controls
        1. header checks
        2. body checks
        3. content filter
        4. allow sender, no fileter nor checks
        5. check postfix responses
        6. postfix check
    4. Configuring amavisd-new
      1. 05-node-id
      2. 05-domain_id
      3. 20-debian_defaults
        1. spamassassin settings
        2. mail notification
        3. banned files
      4. 50-user
        1. recipient delimiter
        2. final spam/virus destiny
      5. backup copy
        1. debug amavis
  3. Pyzor Razor Spamassassin
    1. Pyzor
    2. spamassassin
    3. debug spamassassin
    4. spamassassin for amavis user
    5. dcc
  4. local dns cache
    1. djbdns
    2. bind9
  5. Post Installation
    1. Test the Installation:
    2. Installing ClamAV:
    3. Tweaking Notification Settings:
    4. Back up critical files:
    5. Set up security reports:
    6. Set up intrusion detection:
  6. spam traffic and load
    1. P2 750mhz 512mb
    2. p5 3.5Ghz 512
  7. More Anti-Spam
  8. Support
  9. Sources

Debian Anti-Spam Anti-Virus Gateway Email Server


== Debian Stable ===

** Version 20061118**

Debian Instalation

****************************************************** Debian Installation: Index ****************************************************** The drivers for most network cards got so good, that Debian detects it. In most cases this type of server can run on a PC. Before you start the installation, you may need to know what brand and model your Ethernet card is. You may need to know what chip set the card has. I was unable to install a 3Com 3c509 ISA card.

The fun part of the installation is that no matter how I describe the process to you, it may be different when you do it. The Debian installation process somewhat follows a linear pattern, but I cannot guarantee what order the screens will come up. Because the Installer software itself may be downloaded, and we are using the 'wheezy' version, the Installer software will change frequently. In general, if you are asked questions during installation, the installer guesses what the most appropriate response would be, and it usually is what we want.

If things don't go well and you need to start over, I strongly suggest you delete everything off the hard drive during [Partition a hard drive]. Starting with a clean slate helps a lot.

Additional information on the Debian Installer is located at http://d-i.alioth.debian.org/manual/en.amd64/index.htmll

The main objective of the Debian Installer is to gather enough information to enable it to install the [Debian base system configuration] menu. It needs to know what language to continue in, what keyboard you are using, what network hardware you have (it should figure this out automatically), and what your network settings are (we don't want it to figure this out via DHCP). We will also have to configure the partitions on the hard drive at this time so we have a place to put the software that is installed.

We are going to erase the hard drive so make sure you don't have any data on it you might need. You may have to change the order of boot devices in your BIOS before we begin. Boot up the computer using the Installer CD or the usb Installer. If you use the usb to boot up, you might need to check if your motherboard allows boot from usb. I recommend the CD-ROM. The instructions below pertain to the CD-ROM method in the default "ask as few questions as possible" mode. When the system boots up to the Debian screen, simply press [Enter] at the boot: prompt.

[ !! Choose Language] This determines the language of the installer and picks a keyboard. This installation has only been tested with English - English [Choose country, territory or area] Choose what is appropriate

[! Select a keyboard layout] American English selects a standard qwerty keyboard. Before you select a keyboard, read the next instruction. You need to be prepared in advance to cancel DHCP configuration.

There will be a few screens of activity, then this will come up: [Configuring the network with DHCP] Quickly hit [Cancel] because we want DHCP configuration to fail. (If you are not familiar with your network yet, choose dhcp and later you can change it to static ip) (First time you are doing this use DHCP. It took couple hours to figure out how my "company's" network was structured.

[Module needed by your ethernet card] If you see this menu, it only means one thing. The Installer does not recognize your Ethernet card. Look through the list; the majority of cards that are supported will NOT be on the list, this is a list of somewhat obsolete or possibly bleeding edge cards, not the majority. If it does not find your card, try another NIC Card. This is going to be an email server, so a reliable NIC card is important. In most cases any Intel card will work as they make sure their drivers are in kernel. Broadcom cards might require driver to be downloaded on usb and loaded while installation is looking for drivers. If you have a problem, the fastest way to solve the problem may be to replace the card with another model.

[!! Configure the network] Network autoconfiguration failed

We wanted that to happen, simply press: [Continue]

On the next screen, choose the default of: [Configure network manually]

[!! Configure the network]
Make sure Num Lock is on!
[IP address:]
[Name server addresses:]
444.444.444.444 555.555.555.555
[Domain name:]


Partition the Hard Drive:

Index ****************************************************** The disk partitioning software that comes with this version of the Debian Installer seems to be geared toward novices and as such makes a lot of assumptions in order to make partitioning easy. However, if you want to deviate from what the software provides, it is somewhat cumbersome. At this point you can play with the partitioning software all you like. If you have problems, simply erase the disk and start over. [!! Partition disks]

[Partitioning method:] Choose Guided - use entire disk

[Select disk to partition:] Choose what is appropriate

[Partitioning scheme:] Last thing you want is to be out of space on a partition while there is a plenty of space on the machine. But, you are free to choose any of the three partitioning schemes provided but we will need to research the space for each data partition, or know it from your experience. If you choose the [Separate /home partition] or [Separate /home, /usr, /var, and /tmp partitions] method of partitioning, ideally you would have 14GB or more for either the /var partition or the /var/spool partition respectively. **Use entire disk is preferred. There are many cases where /var will get large do to mail logs, or you need more space to upgrade to newer Debian.

If you are building this with a very small drive (not recommended) or simply want to maximize disk space, choose [All files in one partition]

For a larger drive you may optionally choose but make sure the / is at least 20-30% of the drive: [Separate /home partition] (The only time I separate /home is if I want to install /home on xfs file system)

Once you have what you like, choose [Finish partitioning and write changes to disk] [Write changes to disk?] [Yes]

[! Configure time zone] [Select your time zone:] Simply choose what is appropriate.

[!! Set up users and passwords] This will ask for root's password and allow you to create a "normal" user and a password for that user. Watch your [Num Lock] status. Use really good passwords and don't forget them. Please add one, and just one, normal user here. If you plan on storing mail locally on this machine (not documented here), or even if you don't, create a user who's main purpose in life might be to hold root's mail. I suggest calling the user myuser or something similar. Keep in mind that all the best hacker tools run on Linux. If a hacker gains root access to this box, your entire network is history.

[Installing the base system] Wait....

[! Configure the package manager] [Use a network mirror?] Choose [Yes] [Debian archive mirror country:] Choose your country [Debian archive mirror:] Choose a mirror near you (mirrors.kernel.org works very well in the US) [HTTP proxy information] (configure if needed, otherwise leave unconfigured) Scanning the mirror...

[! Configuring popularity contest] You decide if you would like participate.

[Debian software selection] [Choose software to install:] You only want to select 'Standard system' here (nothing else). Simply [Tab] over and select [Continue]. Do not select 'Desktop environment'. Use the [spacebar] to deselect package groups if needed. Software will download now. I hope you have a fast Internet connection. What software we don't have now, we can easily get later. We are trying to keep this system somewhat clean. We will use apt-get to install most software after the fact. Some software may also be upgraded, and as a result, you may be asked some questions. When asked a question, usually the default answer will be the correct answer.

This may not come up, but in case it does: [Configuring Exim v4 (exim4-config)]

[General type of mail configuration:] choose [no configuration at this time] [Really leave the mail system unconfigured?] [Yes]

[Root and postmaster mail recipient:] The "normal" user we added earlier will display here. This is fine, so simply accept this. Since all mail will be relayed to another server, this setting will actually end up being ignored. However, if you configure your system to store mail locally, all of root's mail will be redirected to this "normal" user's mailbox. This is necessary because you typically cannot access root's mailbox remotely.

[! Install the GRUB boot loader on a hard disk] [Install the GRUB boot loader to the master boot record?] If you would like the install the GRUB boot loader choose [Yes]

[Finish the installation] Remove the CD or usb when prompted, then hit [Continue] This will reboot.

apt-get install ntpdate ssh vim

It may ask you to insert the installation CD; do so, then please remove it afterwards. We installed ntpdate simply to set our clock to the correct time. Later we will disable it from running when our machine boots up and instead use the ntp daemon to keep our clock accurate. Note that if you have problems communicating with the download server (download seems stuck at [0%] - nothing seems to be happening for a long time), you can use [Ctrl]+c to break out of the communication session then try again. You should not use [Ctrl]+c when software is actually installing however, doing so could trash your system.

Thanks to the ntpdate program, our system should now have the correct time. Now we need to set our CMOS clock to the same time as our system:

hwclock --systohc

Once you are back at the shell prompt, reboot the system with [Ctrl][Alt][Delete] or reboot

This is the end of the basic Debian installation.

If you don't feel good about the way things went, or you would like to experiment with one of the other methods of installation, this would be the time to start over from scratch!


PuTTY and additional programs:

Index ****************************************************** Now turn the monitor off and head on over to your trusty old Windows computer. We are going to configure every thing else from there!

You should have this document open in a window on your Windows computer because we are going to use a Windows SSH client called PuTTY to operate our spamfilter remotely. I am going to save you a lot of typing because you are going to select text with the mouse, copy it to the clipboard with [Ctrl]+c and then paste it into the PuTTY window with a right-click of the mouse. This will save you a ton of typing.

Download putty.exe from somewhere like: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

Place putty.exe on your desktop, open it up, select SSH, input the IP address of the spamfilter then enter a name for your session in the Saved Sessions box. In the Category window, expand Terminal and click on Features. Check the box "Disable application keypad mode". Just below this in the Category window, click on Window, and increase "Lines of scrollback" from 200 to 400. Click on Session (at the top), then Save. the "Disable application keypad mode" enables us to use the numeric keypad when using vi.

When you use PuTTY again, simply double click on the saved session. Make sure you are at a command (shell) prompt before exiting PuTTY. You can log off the PuTTY window by issuing the command 'logout' or 'exit' or [Ctrl]+d.

If you are selecting some text to paste onto the Linux command prompt (the bash shell), you normally should not select the empty line below the text we are selecting. If you do, this has the same effect as hitting the [enter] key when it is pasted into the PuTTY screen. Sometimes this is desirable. If you select only to the end of the text, you will have the opportunity to review what was pasted before you hit [enter]. Make sure the command line is empty before you paste something into it.

If you are editing a configuration file (we will use the vi editor to do that), you may select multiple lines to copy and paste. To insure there is a newline character at the end of each line I suggest extending your selection to the empty line below the text you are selecting. I will provide empty lines below any text that ends up getting pasted into a document we are editing with vi.

Some of the text in this document will have to be edited either before or after you copy and paste it into the PuTTY window. If you have not already done so I recommend you save this document as a text file or an html file and do a search and replace of key items like your domain name and IP address, then use that document to continue. I suggest using WordPad or your favorite plain text HTML editor to edit this file. Do not use a program that will modify the HTML code. If you open this document in WordPad there are instructions at the top of the page. Once your changes have been made, open the saved document in your browser. You will now have your own semi custom document.

Note. Your [Home] and [End] keys will work when editing a file using vi, but will not work at the command prompt (you can use [Ctrl]+a and [Ctrl]+e for this).

Open up a PuTTY session now and log in as root. The command prompt at the bash shell will look something like: sfa:~# The ~ (tilde) represents our home directory, and because we logged in as root, our home is /root

This would be a good time to also download and install WinSCP. WinSCP is a great GUI file browser that lets you transfer files between your Windows machine and your new Debian box. You can also edit files on your Debian box from your Windows machine using WinSCP's editor. I suggest when you save sessions you leave the password blank so you are prompted for it each time you log in.

Please install and configure PuTTY and WinSCP per the notes above.

Important note: The machine is very vulnerable at this point. Any time you are not working on the spamfilter, you should unplug the ethernet cable! This machine should be connected to the Internet only when necessary to configure it. We need to get all our security measures in place before it "goes live". You will need to leave it plugged in to complete the installation however. If you are familiar with editing files on a Linux system, it might be a good idea to jump ahead to "Create Firewall Rules" and then return here to continue.


The 2 minute vi tutorial:

Index ****************************************************** We are going to use vi (vim actually) to do most of our editing. Fortunately we only need to learn a few commands to be able to accomplish our tasks. There are 3 operating modes in vi. There is the "Command" mode, the "Write" mode and the "Command line" mode. When you first open a file for editing, you are in Command mode. You change to Write mode by entering the letter "i", (short for "insert"). You can edit text pretty much as you would expect in Write mode. You exit out of Write mode and return to Command mode by hitting the [Esc] key. There are many commands that can be learned in Command mode but we only need to learn two more in addition to "i". Those commands are ":" (a colon) and "/" (a forward slash). The colon is used to enter the third mode, the Command line mode and the slash enables the Search command. When you are in Command line mode, you will see a colon at the bottom of the screen. Here is a list of commands we will use while in Command line mode:

:q    quit (provided you have not made any changes) By the way, the lower case q is used often in *nix as a way to exit a screen.
:q!   exits vi and discards changes (great when you trashed the file and just want to start over!)
:wq   saves the changes and exits vi (write and quit)
:w    saves the current changes but does not exit vi (write)
And in command mode:
G    The capital "G" Goes to the bottom of the page (very handy)

And here is how the Search command works:

/text_to_search_for   moves the cursor to the first occurrence of     text_to_search_for

Once the first occurrence of the text we searched for is found, use a lower case 'n' to find the next occurrence.

That's all we need to know for now! If you would like a cheat sheet for additional commands: http://www.fprintf.net/vimCheatSheet.html and http://amath.colorado.edu/computing/unix/vi/

If you install vim from 'testing', vi may no longer use vim (which is what we actually want), so you may need to point vi to vim: Run this to see which program vi points to: ls -l /etc/alternatives/vi

If it says it is pointing to nvi or other program instead of vim or vim.basic (like this):

Then we need to fix it so it points to (symbolically links to) vim (or vim.basic): mv /etc/alternatives/vi /etc/alternatives/nvi ln -s /usr/bin/vim /etc/alternatives/vi

If you run this again: ls -l /etc/alternatives/vi

You should see that it now links to vim.

Verify System Settings

****************************************************** Verify System Settings: Index ******************************************************


We need to take a look at a few important files to make sure they are accurate.

vi /etc/resolv.conf

Make sure our domain name is at the top, in the form:

search example.com

The file should look something like:

search example.com
nameserver 444.444.444.444
nameserver 555.555.555.555

Repair it if it is not. (Use "i", then edit it). If you made changes, Exit the file with [Esc] : wq If you did not need to change anything, Exit the file with [Esc] : q

hosts file

vi /etc/hosts

The top of file should look something like:    localhost.localdomain    localhost    sfa.example.com    sfa

Repair it if it does not (localhost.localdomain is not required).

Remember, use "i" to insert.

If you made changes, Exit the file with [Esc] : wq If you did not need to change anything, Exit the file with [Esc] : q If you have a mess on your hands, Exit the file with [Esc] : q! and try again.

cat /etc/environment

If the above returns "No such file or directory", then the setting is in /etc/default/locale and you can skip editing this file, otherwise please continue.

vi /etc/environment

Change LANG from a UTF-8 setting: LANG="en_US.UTF-8" this is not required to a non UTF-8 setting: LANG="en_US"

Save and exit the file as before. Note: you can run the command 'locale' to see the current settings. It is best to reboot after changing the /etc/environment file. Changes are not recognized until you at least log out, then back in.


Also edit the mailname files:

vi /etc/mailname

The only entry should be our domain name, i.e. example.com. There is a good possibility that our hostname (sfa) is listed here. It needs to be replaced with our domain name! If you made changes, Exit the file with [Esc] : wq

You could have first just looked at the files with

cat /etc/hostname


cat /etc/mailname

Save or exit as usual.

If you made changes to any of the above files:


You can also use [Ctrl]+d to logout. FYI, to power down the system, the command is: shutdown -h now

Apt-get Settings

****************************************************** Change apt-get settings: Index ******************************************************

I use echo "packagename hold" | dpkg --set-selections to place package 'packagename' on hold and echo "packagename install" | dpkg --set-selections to allow it to upgrade.


This next file is critical to the way our system functions. I suggest you read the notes above before you continue. Note that since we are install etch, the default priority for etch is 500.

vi /etc/apt/preferences

Enter this text in the file ("i" to insert) EXACTLY as shown. Yes, you can select the text with your mouse, hit [Ctrl]+c , and then right-click in the vi editor window.

Package: *
Pin: release a=stable
Pin-Priority: 600

Package: *
Pin: release a=testing
Pin-Priority: 450

Package: *
Pin: release a=unstable
Pin-Priority: 400

Exit the file with [Esc] : wq as usual.

We set our 'etch' release to a Pin-Priority of 600. This means that 'stable' software will be installed by default. If you would rather configure the system from a 'testing' base, you should consider using other documents. Sarge based

I recommend you use apt-get -s install [package] before you install any package. It lets you "simulate" what would happen. You will find that apt-cache policy [package] is also helpful. If you want a package that is an 'unstable' version (or any version that is not top priority), you would have to specifically request the 'unstable' version or change the priority before you install it (unless the only version is 'unstable' or your current version is 'unstable'). For example apt-get -t unstable install [package] will install the package and also satisfy dependencies from 'unstable'. If you use apt-get install [package]/unstable then apt will try to meet any dependencies from 'testing'. If you use tools like tasksel, you may have to temporarily change the priority prior to installing a new set of packages. The most stable situation is to only upgrade to new packages if a security flaw is found and make sure you have the ability to completely restore the hard drive if upgrades don't go well. So I don't frighten you too much, the Debian package maintainers are amazing, so apt-get usually works very well.

Use   apt-cache   to search the local database for available packages.
apt-cache search [search terms]   will find packages that sound like what you want and:
apt-cache show [packagename]   will return more details on a particular package.
apt-cache showpkg [packagename]   will return more details on a particular package.
apt-cache policy [packagename]   will return which versions are available along with the priority of each version.
apt-setup   will enable you to change mirrors. The alternative is to edit   /etc/apt/sources.list   manually (which I prefer).
apt-get clean clears the local repository of all retrieved package files.
apt-get autoclean clears the local repository of retrieved package files of programs that are no longer installed.
dpkg -l [packagename] will list the version and a short description of the package we have installed.

You can also search for packages at http://www.debian.org/distrib/packages. At a later time you can study these great instructions for searching your local package database: http://newbiedoc.sourceforge.net/tutorials/apt-get-intro/info.html.en Also grab http://www.oreilly.com/catalog/linuxnut4/chapter/ch05.pdf for later review.

We need to add an 'unstable' source to our list of available Debian packages. Once etch becomes 'stable', we can add a 'testing' source also. This modification is critical to the way our system functions.

cp /etc/apt/sources.list /etc/apt/sources.backup

This creates a backup file. Then:

vi /etc/apt/sources.list

At this point, the contents of the file may look something like this:

# deb cdrom:[Debian GNU/Linux testing _Etch_ - Official Snapshot i386 Binary-1 (20061111)]/ etch main

deb cdrom:[Debian GNU/Linux testing _Etch_ - Official Snapshot i386 Binary-1 (20061111)]/ etch main

deb http://mirrors.kernel.org/debian/ etch main
deb-src http://mirrors.kernel.org/debian/ etch main

deb http://security.debian.org/ etch/updates main
deb-src http://security.debian.org/ etch/updates main

We need to modify this file so the result will look something like this:
(with only the http server unique to your particular system)

deb http://mirrors.kernel.org/debian/ etch main non-free contrib
deb-src http://mirrors.kernel.org/debian/ etch main

deb http://security.debian.org/ etch/updates main
deb-src http://security.debian.org/ etch/updates main

deb http://mirrors.kernel.org/debian/ unstable main non-free contrib
deb-src http://mirrors.kernel.org/debian/ unstable main

Note what I have done here: Any lines that use the cdrom #deb cdrom:[Debian GNU/Linux testing _etch_ have been erased. ([up-arrow] to the top of the file and hold down the [Delete] key.) The 2 'unstable' lines have been copied from the top 2 'etch' lines, and then modified slightly as indicated. The words "non-free" and "contrib" have been added to 2 of the lines. You are welcome to simply copy and paste what I have listed above. Save and exit the file.

Here's a hint on how to quickly make a copy of the first 2 lines: Enter "i" to get into write mode, highlight the 2 lines with your mouse then right click your mouse in the PuTTY window.

It may be necessary to increase the apt cache limit: echo 'APT::Cache-Limit "25165824";' >> /etc/apt/apt.conf

I also suggest adding gnupg keys for a few of the apt sources to apt: gpg --keyserver subkeys.pgp.net --recv-key A70DAF536070D3A1 gpg --armor --export A70DAF536070D3A1 | apt-key add - gpg --keyserver subkeys.pgp.net --recv-key EA8E8B2116BA136C gpg --armor --export EA8E8B2116BA136C | apt-key add - gpg --keyserver subkeys.pgp.net --recv-key 7EF7FFF4276981F4 gpg --armor --export 7EF7FFF4276981F4 | apt-key add -

You must run apt-get update next.

apt-get update

If you have any problems, please check for errors in your sources.list file and run apt-get update again.

We need to remove some programs for security reasons. Hopefully you don't need printer support. This server will not need dial-up support either. apt-get remove lpr nfs-common pidentd portmap

If you are using a multi-processor machine, then use a multi-processor kernel! To locate available smp kernels for etch, you could run: apt-cache search linux-image | grep smp | grep linux-image

If you are running a 2.6.17 (etch) kernel, and have a dual core Intel system, you could for example use the 'linux-image-2.6-686-smp' kernel. You would pick the kernel that most closely matches your system (and your current kernel). To install it, you would simply run: apt-get install linux-image-2.6-686-smp

If you were to install a new kernel, please reboot afterwards.


Index ****************************************************** A quick word about less. less is a great file and directory viewer. You can [page-up] and [page-down] and search for text in the same manner you search for text using vi. Use a lower case "q" to exit less. To view a file using less: less /path/file To view directory contents, pipe it through less: ls -l | less (current directory, or) ls -l /path/directory | less

I also like this one: history | less then enter an upper case G to go to the bottom of the display. It displays the commands you have entered previously. Use q to quit. You can even search the same way you do with vi.

I don't mean to break your concentration, but there is another cool tool called locate. locate allows you to search a database of every file name on the system. It's kind of like Windows Find. You first have to build the database with the updatedb command, and then you can search through it. Try this: we are going to use locate and less together: updatedb locate kmap | less What you are looking at is every keymap file on the system along with any file name that has the string "kmap" in it. Play with it; then "q" to exit less Now we are going to do something cool. Take your mouse and highlight any directory you see above, only highlight the directory and not past it. For example: /usr/share/keymaps/i386/qwerty/ Now right click your mouse anywhere on the screen. You will notice the text has been pasted to the command line. Now [left-arrow] over to the beginning of the line (or hit [Ctrl]+a) and type in: cd Put a space after cd and hit [return]. We just saved ourselves having to type the entire path name just in order to change to that directory. I like that. OK, simply enter cd to get back home.

Sorry for the diversion.

Firewall Rules

****************************************************** Create Firewall Rules: Index ****************************************************** We need to set up some form of firewall on this box. This is a subject that could (and does) fill volumes. We are going to use something quick and simple that will give us a basic firewall. Something is MUCH better than nothing, and we just don't have time to read volumes on the subject right now.

I worked for a couple days trying to figure out what iptables was all about. I tried using tools like lokkit and shorewall and others, only to get frustrated and confused because I kept getting errors and the firewall simply would not work. My best guess is iptables did not like any rules file it did not create itself. Lokkit was a snap in Red Hat, and a nightmare in Debian. That's pretty much how this whole experience went. But I'm learning a LOT more about GNU/Linux by working with Debian. After day 2 it dawned on me iptables is somewhat like Cisco access lists (which I am a little familiar with).

I am going to give you a set of commands below that I want you to paste into the command line, in the correct order. You MUST change the IP addresses to fit your needs, if you have not already done so. The line with '--dport 22' on it is SSH and the network address to the left needs to be the network that both your computer and the spamfilter computer are on. You could also limit access to a single computer (yours, of course) by using your_ipaddress_goes_here/32. This is a security measure. If you do that part wrong, it will lock you out. The lines with '--sport 53' on them are for access to DNS servers. BTW, all you have to do to change your DNS servers is change the entries in /etc/resolv.conf.

If you would like to add more rules in the future or make modifications, simply copy and paste these lines into a text editor like notepad, make the changes you would like, and then copy and paste them to a command prompt in your PuTTY window. You can copy and paste all the lines at once. The first line deletes all the entries that were in the rule-set previously and the next to the last line saves the new rule set. The last line shows how one would load a rules file into iptables. Keep a copy of the text file on your computer and call it firewall-rules.txt. I learned to never edit the /etc/firewall-rules file directly on the spamfilter computer. It looks like iptables will reject the file if anyone other than itself has modified it.

DO NOT USE AS IS, CHANGE NETWORK ADDRESS FIRST IF YOU HAVE NOT ALREADY DONE SO: You can copy and paste this whole section to the command prompt:

iptables -F
iptables -N FIREWALL
iptables -F FIREWALL
iptables -A INPUT -j FIREWALL
iptables -A FIREWALL -p tcp -m tcp --dport 25 --syn -j ACCEPT
iptables -A FIREWALL -p tcp -m tcp -s --dport 22 --syn -j ACCEPT
iptables -A FIREWALL -i lo -j ACCEPT
iptables -A FIREWALL -p udp -m udp --sport 53 -j ACCEPT
iptables -A FIREWALL -p tcp -m tcp --sport 53 -j ACCEPT
iptables -A FIREWALL -p udp -m udp --dport 123 -j ACCEPT
iptables -A FIREWALL -p udp -m udp --sport 6277 -j ACCEPT
iptables -A FIREWALL -p udp -m udp --sport 24441 -j ACCEPT
iptables -A FIREWALL -p tcp -m tcp --syn -j REJECT
iptables -A FIREWALL -p udp -m udp -j REJECT
iptables-save > /etc/firewall-rules
iptables-restore < /etc/firewall-rules

Now run:

iptables -L

To list the rule set. This is informational only.

We have written the firewall rules to a file on the spamfilter computer, but iptables starts with an empty rule set each time the computer restarts. The rule set we saved to /etc/firewall-rules must be "loaded" into iptables every time the system starts up.

We are going to insert the command to configure iptables into a file that starts up the network interfaces when the system boots up:

vi /etc/network/interfaces

And insert the following text (remember, it's "i" to insert) in the blank line just below "iface lo inet loopback":

pre-up iptables-restore < /etc/firewall-rules

Save and exit the file as usual with [Esc] : wq From now on I will assume you know how to edit, save, and exit files using vi. If not stated, it will be implied that after editing a file, you need to save and exit it, or if necessary, discard changes and start over. Please don't think this is where you would stick any old command you would like. This is not the place, and not the way, to do so. That's a whole 'nuther subject. This file is the right place (along with /etc/resolv.conf) to change network settings however.

That's all there is to it. You have just used what I believe is the fewest possible steps to create a simple functional personal firewall for this machine. I will admit that it should have been a lot easier by utilizing one of the firewall tools, but it just didn't work out.

At this point our firewall allows external users to connect to SSH and Mail. It also allows replies from Pyzor, DCC, DNS servers and NTP servers. It blocks (I hope) everything else except any sessions that originate from us. This allows us to connect to the outside world. This box should be behind another firewall at any rate. If so, that firewall/screening router will need to be configured to allow tcp port 25 traffic to this machine, but only after this box is fully functional. If you have things locked down really tight; take a look at http://flakshack.com/anti-spam/wiki/index.php?page=Provide+firewall+access for some ideas. Keep in mind we also need udp port 24441 for Pyzor and access to external DNS servers. As far as DCC, Razor and Pyzor go, try them before you start messing with your Internet firewall. I have my spamfilter behind a screening router, a hardware firewall, and software NAT box firewall and none of them required reconfiguration for these programs to work. Port 25 SMTP will probably need to be opened however.

If you have not done so, reboot again and run

iptables -L

to verify the firewall loaded during start up.

If you have problems, enter the command iptables -F from the console to clear out iptables. This will allow you another shot at it.

Disable Unnecessary Daemons

****************************************************** Disable Unnecessary Daemons: Index ****************************************************** We are now going to remove some services (daemons) that start up at boot time. I only want you to remove the services I have listed below, no more than that. You could (and probably would) end up with an unusable system if you disabled more than this. Our basic system does not start up many services anyway but "you can't hack a service that isn't running". The only secure system is a system that doesn't exist.

Below is a list of commands I found useful to determine what services were running. Run them one at a time if you care to. top

ps afx
ps afxl
ps -A
ls -F /etc/rc2.d
lsof -i | grep LISTEN
lsof -P | grep LISTEN
netstat -pn -l -A inet
netstat -pn -l inet

These are from http://linuxgazette.net/issue89/gonzales.html#4

I also liked the lsconfig script I found here: http://www.shallowsky.com/software/scripts/lsconfig Save it as /usr/bin/lsconfig and make it executable. Like this: cd /usr/bin wget http://www200.pair.com/mecham/debian/lsconfig chmod +x /usr/bin/lsconfig lsconfig If you run lsconfig, the stuff just scrolls by on the screen. You can choose "Copy all to Clipboard" from the drop down menu of the PuTTy window. Click on the two little computers in the upper left-hand corner of the PuTTY window to access the menu. Then open a spreadsheet and paste it into it. Play with it from there.

We need to make a backup of the init scripts in /etc/init.d because after we remove some services, the system may delete the scripts.

cp -r /etc/init.d /etc/init.d-original

These commands assume you are not hooking up a printer to this machine and you are not using a laptop to build your spamfilter! Feel free to copy and paste these next two boxes in their entirety.

Ok, let's just get this done:
/etc/init.d/lpd stop
update-rc.d -f lpd remove
/etc/init.d/nfs-common stop
update-rc.d -f nfs-common remove
/etc/init.d/portmap stop
update-rc.d -f portmap remove
/etc/init.d/pcmcia stop
update-rc.d -f pcmcia remove
/etc/init.d/ppp stop
update-rc.d -f ppp remove
/etc/init.d/exim4 stop
update-rc.d -f exim4 remove
update-rc.d -f ntpdate remove

The inetd service (InterNET Daemon) starts multiple services that can be enabled or disabled individually. update-inetd --disable time update-inetd --disable daytime update-inetd --disable echo update-inetd --disable chargen update-inetd --disable ident update-inetd --disable discard

The last one may ask you a question regarding "multiple entries", answer yes (y).

Restart the service: /etc/init.d/inetd restart

Check that we got everything:

lsof -i | grep LISTEN

The only daemon you should see is at this point is *:ssh

You may have to run this again: update-inetd --disable discard

If there are other programs shown, try rebooting and test again.

If you would like to get any of these services back, we can reverse the events. For example, to enable 'ident' and then refresh inetd, you could issue these 2 commands:

update-inetd --enable ident /etc/init.d/inetd restart

For example, to re-enable the printer service, and start it up right now:

update-rc.d lpd defaults /etc/init.d/lpd start

If you get an error that the file does not exist, first restore it from the backup we made, and then try again:

cp -i /etc/init.d-original/lpd /etc/init.d update-rc.d lpd defaults /etc/init.d/lpd start

This is an example only, we actually uninstalled printer support.

We have just made our machine much more secure than when we started. I will talk about additional security measures at the end of this document, but we want to get this thing up and running first! We want to see this puppy actually do something! You used a few commands above to help you see what services were running before we made changes. Run them again, if you like, to see the effect of disabling them.

Configure NTP

****************************************************** Configure the NTP daemon: Index ****************************************************** Install the program:

apt-get install ntp-simple

This program may be deprecated, if so, instead run:

apt-get install ntp

We actually may not need to configure the ntp daemon (ntpd). We installed ntp-simple which does a good job of setting everything up for us. It is set up to use a different time server each time the daemon starts up (http://www.pool.ntp.org/). It configures our machine as an ntp client. If you have a favorite ntp server that you wish to use you can edit /etc/ntp.conf and insert it per the example in the file. NTP is a flexible and complex system so I leave it up to you to research it further if you care to. If you care to choose your own servers from the list of Public NTP Secondary (stratum 2) Time Servers at http://www.eecis.udel.edu/~mills/ntp/clock2a.html we can use the little ntpdate program to quickly test them prior to insertion in /etc/ntp.conf:

For example:

/etc/init.d/ntp-server stop
ntpdate clock.fmt.he.net
ntpdate ntp1.tummy.com
/etc/init.d/ntp-server start

By the way, the command to modify the date and time is date and to change the time zone it's tzconfig

If you are using the etch CD, our default system editor will be nano, and not vim. We need soon need to edit a system file called crontab but we don't want to have to learn another new editor so we will change our default system editor: vi /root/.profile

and just below the line "fi" insert this entry: export EDITOR=/usr/bin/vim

Save and exit the file, then logout of PuTTY, then connect back in.

Installing Programs

We need to install a number of additional programs. Go ahead and select ALL the text in the box below with your mouse, then use [Ctrl]+c to copy it to the clipboard, then right-click the PuTTY window, then hit [enter] to issue the command. I suggest you select from right to left (bottom to top). Going the other way always wants to select one extra space character which can be a problem with apt-get commands.

apt-get install arc arj autoconf automake1.7 bzip2 cabextract db4.3-util libarchive-tar-perl libarchive-zip-perl libauthen-sasl-perl libberkeleydb-perl libconvert-binhex-perl libconvert-tnef-perl libconvert-uulib-perl libdb4.3-dev libdbd-mysql-perl libdbi-perl libdigest-hmac-perl libdigest-sha1-perl libhtml-format-perl libhtml-parser-perl libhtml-tagset-perl libhtml-tree-perl libio-multiplex-perl libio-socket-ssl-perl libio-string-perl unrar-free arj

And there are more:

apt-get install libio-stringy-perl libio-zlib-perl libldap2 libmail-spf-query-perl libmailtools-perl libmime-perl libnet-dns-perl libnet-ident-perl libnet-ldap-perl libnet-perl libnet-ph-perl libnet-server-perl libnet-snpp-perl libnet-telnet-perl libsocket6-perl libtimedate-perl libtool libunix-syslog-perl liburi-perl libwww-perl lsof lynx lzop make ncftp nomarch pax perl-doc rblcheck unzip unzoo zip zlib1g-dev zoo pyzor razor libcompress-zlib-perl gnupg

For lha license information see http://lists.debian.org/debian-devel/1999/11/msg00549.html and for rar (unrar) see http://www.rarsoft.com/index.htm

This is a new system, so let's make sure everything is current. First, run a simulation:

apt-get -s upgrade

Then if everything is as you might expect:

apt-get upgrade

Upgrading certain programs may bring up dialog boxes requiring you to respond to configuration questions. Typically, the default answers are [ENTER].

If the kernel is upgraded, once the upgrade process is complete, you must: reboot

We are using apt-get to download and install most of our core programs. Note that when we install Postfix, apt-get is smart enough to remove exim4 (because it conflicts with Postfix). This document is based of the following versions of these programs: postfix 2.2.x spamassassin 3.1.x amavisd-new 2.4.4. The instructions may differ significantly if newer (or older) versions are installed. Please run:

apt-cache policy postfix spamassassin

This will give output similar to the following:

  Installed: (none)
  Candidate: 2.3.3-1
  Version table:
     2.3.4-1 0
        400 http://mirrors.kernel.org unstable/main Packages
     2.3.3-1 0
        500 http://mirrors.kernel.org etch/main Packages
  Installed: (none)
  Candidate: 3.1.7-1
  Version table:
     3.1.7-1 0
        500 http://mirrors.kernel.org etch/main Packages
        400 http://mirrors.kernel.org unstable/main Packages

This tells us that the etch versions of Postfix and SpamAssassin will be installed. If we wanted to install the unstable versions, we would have to override the choices, e.g. apt-get install [packagename]/unstable, or if necessary apt-get -t unstable install [packagename]. Note that another option is to momentarily make unstable the highest priority in /etc/apt/preferences, then override what will be installed, e.g. apt-get install [packagename]/testing. Read this. There is a Debian version of amavisd-new available, but we are NOT going to install it. The configuration files for newer Debian (testing/unstable) versions of amavisd-new are not consistent with the typical way amavisd-new is configured. Instead of one configuration file, the newer Debian versions split the configuration files into half a dozen files in a couple different directories. We will instead install amavisd-new from the original author. So with this in mind: Read instructions above before you proceed.

apt-get install spamassassin

If you would like to install the unstable version of SpamAssassin, you should do it like so: apt-get install spamassassin/unstable

apt-get install postfix postfix-pcre postfix-mysql postfix-ldap

Debconf will pop up a Postfix configuration screen.

For [General type of configuration?] select:
No configuration

Installing Amavisd-new


apt-get install amavisd-new

If (and only if) you already have amavisd-new installed, you need to remove it (this will not remove your configuration files which is a good thing). First make sure amavisd-new is the only thing that will be removed by 'simulating' the removal: apt-get -s remove amavisd-new

If it is, then remove it: apt-get remove amavisd-new

If it is not, then you must make a note of any and all programs that will be removed, because you will have to reinstall them. Good luck with all that. ;)

Here are all the steps needed to install amavisd-new. Some of the files it tries to delete or copy may not be on your system but there is no need to panic if it fails to find them. The last few dpkg-statoverride commands will also fail if you have ever installed Debian amavisd-new - but this is not an issue either. We are going to place files in the same place the Debian version of amavisd-new would have. adduser --group --system --home /var/lib/amavis --shell /bin/sh amavis mkdir /var/run/amavis chown amavis:amavis /var/run/amavis mkdir /etc/amavis mkdir /etc/amavis/en_US mkdir /var/lib/amavis/tmp mkdir /var/lib/amavis/db mkdir /var/lib/amavis/var mkdir /var/lib/amavis/virusmails chown -R amavis:amavis /var/lib/amavis chmod -R 750 /var/lib/amavis cd /etc/amavis wget http://www200.pair.com/mecham/amavisd/2.4.4/amavisd.conf

Did you get that wget download OK? If you did, then continue on. If not, then you won't be able to get other downloads from me, so you have a major problem.

wget http://www200.pair.com/mecham/amavisd/2.4.4/amavisd.conf-sample ln -s /etc/amavis/amavisd.conf /etc/amavisd.conf

cp -r /etc/amavis/en_US /etc/amavis/en_US-backup cd /etc/amavis/en_US rm charset rm template-dsn.txt rm template-spam-admin.txt rm template-spam-sender.txt rm template-virus-admin.txt rm template-virus-recipient.txt rm template-virus-sender.txt wget http://www200.pair.com/mecham/amavisd/2.4.4/en_US/charset wget http://www200.pair.com/mecham/amavisd/2.4.4/en_US/template-dsn.txt wget http://www200.pair.com/mecham/amavisd/2.4.4/en_US/template-spam-admin.txt wget http://www200.pair.com/mecham/amavisd/2.4.4/en_US/template-spam-sender.txt wget http://www200.pair.com/mecham/amavisd/2.4.4/en_US/template-virus-admin.txt wget http://www200.pair.com/mecham/amavisd/2.4.4/en_US/template-virus-recipient.txt wget http://www200.pair.com/mecham/amavisd/2.4.4/en_US/template-virus-sender.txt

cd /usr/local/src wget http://www.ijs.si/software/amavisd/amavisd-new-2.4.4.tar.gz tar xzvf amavisd-new-2.4.4.tar.gz cd amavisd-new-2.4.4 test -e /usr/sbin/amavisd-new && cp /usr/sbin/amavisd-new /usr/sbin/amavisd-new-debian cp amavisd amavisd-new

cp amavisd-new /usr/sbin/amavisd-new cp amavisd-new /usr/sbin/amavisd-new-2.4.4 cd /etc/init.d wget http://www200.pair.com/mecham/debian/amavis-init-20030616 mv amavis-init-20030616 amavis chmod +x amavis update-rc.d amavis defaults cd /etc/cron.daily wget http://www200.pair.com/mecham/crondaily/amavisd-new.txt mv amavisd-new.txt amavisd-new chmod +x amavisd-new cd /etc/cron.d wget http://www200.pair.com/mecham/crond/amavisd-new.txt mv amavisd-new.txt amavisd-new dpkg-statoverride --add amavis amavis 755 /var/lib/amavis dpkg-statoverride --add amavis amavis 755 /var/lib/amavis/virusmails dpkg-statoverride --add amavis amavis 755 /var/run/amavis

Postfix Configuration Part 1

****************************************************** Postfix Configuration Part 1: Index ****************************************************** We need some sample files from the Postfix source code. cd /usr/local/src

Change these next lines to match the version of Postfix you have: wget http://ftp.debian.org/debian/pool/main/p/postfix/postfix_2.3.3.orig.tar.gz tar xzvf postfix_2.3.3.orig.tar.gz

We always place our source code in /usr/local/src.

List the contents of this directory: ls -l

We have created a new subdirectory and unpacked the source code into it. Mine is called postfix-2.3.3. We don't need to keep the compressed file. Make sure you are still in the /usr/local/src directory, then remove the compressed file with the command: rm postfix*

You will get an error like "rm: cannot remove `postfix-2.3.3': Is a directory". That's good; we didn't want to remove the directory.

When we downloaded our Postfix source code, a number of sample files were included. We want to make use of those sample files so we will copy them to the postfix directory. The second line below may need to be edited if your version of the Postfix source code is different than mine. MAKE SURE you answer "n" to "overwrite?" Do each section separately.

cp -i /usr/share/postfix/main.cf.debian /etc/postfix/main.cf

cp -i /usr/local/src/postfix-2.3.3/conf/* /etc/postfix

cp -i /etc/postfix/header_checks /etc/postfix/body_checks

cp -i /etc/postfix/access /etc/postfix/sender_access


****************************************************** Edit master.cf: Index ****************************************************** Read this before you complete this section. If you are using Postfix version 2.1.x, 2.2.x or 2.3.x I have done the work of configuring master.cf for you and you may simply download the file from me. If you wish to use this file, follow the first 4 steps below.

The master.cf we download here can be used with Postfix versions 2.3.x, 2.2.x and 2.1.x

postfix stop
cd /etc/postfix
mv master.cf master.cf-original
wget http://www200.pair.com/mecham/debian-postfix-2.3-amavisd/master.cf

Note that wget will not normally overwrite an existing file, so we "moved" master.cf to another file first. Now you can simply jump to Edit Main.cf:

If you wish to do the work yourself, continue on.

postfix stop
vi /etc/postfix/master.cf

Next, we want to give Postfix some information it will need to talk to the amavisd-new program. (BTW, watch out for the two Postfix configuration files, both located in the /etc/postfix folder. More than one admin has gotten confused between "master.cf" and "main.cf"!) Add these lines near the bottom of master.cf. Note: the items on these lines are separated by tabs. And the "-o" is the lower case letter o, not zero. These settings are from http://www.ijs.si/software/amavisd/README.postfix. You can copy and paste this entire section once the cursor is in the correct position (see below) and you are in insert mode. Note: when copying sections like this that contain tabs, rather than using a right click of the mouse to paste into the editor, press [Shift]+[Insert]:

smtp-amavis    unix    -    -    -    -    2    smtp
    -o smtp_data_done_timeout=1200
    -o smtp_send_xforward_command=yes
    -o disable_dns_lookups=yes
    -o max_use=20    inet    n    -    -    -    -    smtpd
    -o content_filter=
    -o smtpd_restriction_classes=
    -o smtpd_delay_reject=no
    -o smtpd_client_restrictions=permit_mynetworks,reject
    -o smtpd_helo_restrictions=
    -o smtpd_sender_restrictions=
    -o smtpd_recipient_restrictions=permit_mynetworks,reject
    -o smtpd_data_restrictions=reject_unauth_pipelining
    -o smtpd_end_of_data_restrictions=
    -o mynetworks=
    -o smtpd_error_sleep_time=0
    -o smtpd_soft_error_limit=1001
    -o smtpd_hard_error_limit=1000
    -o smtpd_client_connection_count_limit=0
    -o smtpd_client_connection_rate_limit=0
    -o smtpd_milters=
    -o local_header_rewrite_clients=
    -o local_recipient_maps=
    -o relay_recipient_maps=
    -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks

We also need to add two items below the 'pickup' service type. The 'pickup' service 'picks up' local mail (local meaning "on this machine") and delivers it. Later we will create a daily/weekly report that this box will mail to us and because the report will contain contents that will classify the report itself as spam, this is a way to bypass content filtering for mail generated by this machine. Add this just below the 'pickup' service type:

    -o content_filter=
    -o receive_override_options=no_header_body_checks

When you are all done, the table and the lines right after it should end up looking like this:

# ==========================================================================
# service type  private unpriv  chroot  wakeup  maxproc command + args
#               (yes)   (yes)   (yes)   (never) (100)
# ==========================================================================
smtp      inet  n       -       -       -       -       smtpd
#  -o receive_override_options=no_address_mappings
#submission inet n       -       -       -       -       smtpd
#  -o smtpd_enforce_tls=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#smtps     inet  n       -       -       -       -       smtpd
#  -o smtpd_tls_wrappermode=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#628      inet  n       -       -       -       -       qmqpd
pickup    fifo  n       -       -       60      1       pickup
    -o content_filter=
    -o receive_override_options=no_header_body_checks
cleanup   unix  n       -       -       -       0       cleanup
qmgr      fifo  n       -       n       300     1       qmgr
#qmgr     fifo  n       -       -       300     1       oqmgr
tlsmgr    unix  -       -       -       1000?   1       tlsmgr
rewrite   unix  -       -       -       -       -       trivial-rewrite
bounce    unix  -       -       -       -       0       bounce
defer     unix  -       -       -       -       0       bounce
trace     unix  -       -       -       -       0       bounce
verify    unix  -       -       -       -       1       verify
flush     unix  n       -       -       1000?   0       flush
proxymap  unix  -       -       n       -       -       proxymap
smtp      unix  -       -       -       -       -       smtp
# When relaying mail as backup MX, disable fallback_relay to avoid MX loops
relay     unix  -       -       -       -       -       smtp
    -o fallback_relay=
#       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq     unix  n       -       -       -       -       showq
error     unix  -       -       -       -       -       error
discard   unix  -       -       -       -       -       discard
local     unix  -       n       n       -       -       local
virtual   unix  -       n       n       -       -       virtual
lmtp      unix  -       -       -       -       -       lmtp
anvil     unix  -       -       -       -       1       anvil
scache    unix  -       -       -       -       1       scache
smtp-amavis    unix    -    -    -    -    2    smtp
    -o smtp_data_done_timeout=1200
    -o smtp_send_xforward_command=yes
    -o disable_dns_lookups=yes
    -o max_use=20    inet    n    -    -    -    -    smtpd
    -o content_filter=
    -o smtpd_restriction_classes=
    -o smtpd_delay_reject=no
    -o smtpd_client_restrictions=permit_mynetworks,reject
    -o smtpd_helo_restrictions=
    -o smtpd_sender_restrictions=
    -o smtpd_recipient_restrictions=permit_mynetworks,reject
    -o smtpd_data_restrictions=reject_unauth_pipelining
    -o smtpd_end_of_data_restrictions=
    -o mynetworks=
    -o smtpd_error_sleep_time=0
    -o smtpd_soft_error_limit=1001
    -o smtpd_hard_error_limit=1000
    -o smtpd_client_connection_count_limit=0
    -o smtpd_client_connection_rate_limit=0
    -o smtpd_milters=
    -o local_header_rewrite_clients=
    -o local_recipient_maps=
    -o relay_recipient_maps=
    -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks
#   -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks,no_address_mappings

(Don't worry about the stuff below this part displayed above - you won't need to change any of those rows, and they are all listed as "pipe" in the last column.)


****************************************************** Edit main.cf: Index ****************************************************** Our next friend is the file /etc/postfix/main.cf the main configuration file for Postfix. Following are suggested values to use in main.cf. These have been tested for this configuration and will work fine, but there are many judgment calls involved in this, and it is a good idea at some point to learn more about Postfix configuration, on your own. You could first look at the sample Postfix main.cf file /usr/share/postfix/main.cf.dist . There are comments describing some of the most common options. Refer also to the Postfix documents on your machine in the /usr/local/src/postfix-2.2.x/README_FILES directory, or read the documentation on the Postfix web site http://www.postfix.org/documentation.html. I also recommend http://www.postfix-book.com/.

Since we are setting up our spamfilter to relay all of its mail to another server, we will be using what Postfix considers a "relay domain address class" which essentially means that we will use, out of the 300+ configurable parameters in Postfix, a small group of parameters that serves our purpose best. This address class is described here: http://www.postfix.org/ADDRESS_CLASS_README.html#relay_domain_class. We are also acting as a primary MX for another server so please read this appropriate section: http://www.postfix.org/STANDARD_CONFIGURATION_README.html#backup

It is common in Postfix to store items in lookup tables. We are going to use several hash tables to store data that Postfix will use. Once we have plain text data in these tables, we use the postmap command to create binary files (Berkeley DB format) that Postfix will ultimately use to retrieve the data. For example, if you have a file called "filename" and you "postmap filename", a new file is created "filename.db". Postfix will retrieve data from "filename.db", not "filename". There are more than a dozen other types of data files that Postfix can use to store data. Hash tables are an appropriate choice for several tables we will use, and pcre (Perl Compatible Regular Expressions) is appropriate for a couple tables we will use to hold content filtering data. In its simplest form a hash table is comprised of 2 pieces of data, a key and a value; typically referred to as the key/value pair. The key and the value are separated with whitespace (typically a space or tab). The data in a typical table that we use in Postfix would look something like: user1@example.com OK user2@example.com OK user1@example2.com OK Suggested reading: http://www.postfix.org/DATABASE_README.html

OK, lets get going. Note: in commands, wherever quote marks " " are used, use them. Rather than editing main.cf directly (which you may nonetheless do, if you prefer) we'll use a handy tool that comes with Postfix, named "postconf". We will use the -e switch, which means to "edit" main.cf.

aliases www to postmaster

We simply need to make a correction to the default setting here:

postconf -e "alias_maps = hash:/etc/aliases"

Now we will create from the text version of the aliases file, the binary version that Postfix will actually use. We do not need to edit the aliases file at this time but it would be a good idea to do so simply to view the contents. You need to run newaliases now, and every time after you edit the aliases file. The newaliases command is just like postmap except that it's specific to the aliases file.


You will see there is now an "aliases.db" file in /etc/. That is what Postfix reads. Now that you have a proper aliases file, it appears that because we are going to configure our system to relay all mail (no mail will be locally delivered), the aliases file will be ignored by Postfix. We instead will set up virtual_alias_maps that we can use for address rewriting should we need to. Other programs may read/write to the /etc/aliases file, so we do not remove it.

myorgin domain and network

myorigin The domain name that mail created on this machine appears to come from. For example, if one of our programs (cron for example) sends mail to "root" it will be sent to "root@example.com".

postconf -e "myorigin = example.com"

Obviously, in the above, and all the following commands, replace my example parameters, like "example.com", with your own specific values.

myhostname The fully-qualified domain name (FQDN) of the machine running the Postfix system.

postconf -e "myhostname = sfa.example.com"

mynetworks These are the machines I trust, and will relay mail for, to any destination. Generally, this is set to my LAN, or just one, or a few trusted internal mail servers. Along with "relay_domains", this is an important one to get right lest you run the possibility of becoming an "open relay". In other words, your box could accept and forward mail to domains for which it has no business doing so. Being an open relay is a serious issue, and can cause you to get blacklisted by various Internet anti-spam lists, among other problems. You can specify a single computer, multiple individual computers, or any computer on a specified network. You can also exclude certain hosts in your network by preceding the IP address with an exclamation point. Excluded addresses need to be listed before included addresses. If you are using a NAT router that substitutes the real client IP address with its own, then you must exclude the IP address of the NAT router from mynetworks. If you will be dealing with multiple internal mail servers, and/or want to allow several machines and/or subnets to relay through this server (careful!), just add them to this parameter in CIDR format, like this: Please read important notes above.

postconf -e "mynetworks =,,"

The above will allow the machines on the networks, and to relay smtp mail through this box. You could also specify a single computer's IP address. If you only know your dotted decimal netmask (i.e. and need to convert it to CIDR format, try the http://www.wildpackets.com/products/free_utilities/ipsubnetcalc/overview. (Input an IP address on your network, select the subnet info tab, select your subnet mask, your network is Subnet ID/Mask Bits.) Or simply take a look at http://www.belchfire.net/webtools/cidr_conversion_table.html.

message size

message_size_limit Maximum size email that Postfix will let in the "front door".

postconf -e "message_size_limit = 10485760"

The above allows email up to 10MB, the value is in bytes (10*1024*1024). Mail larger than this may possibly get bypassed by the anti-virus scanner (ClamAV). You could increase this if you also configure ClamAV to scan files larger than 10MB (or disable the limit in clamd.conf). I'm really not sure, but if any process keeps the entire message in RAM while it is being processed, and you get a lot of large messages in a short time period, and you allow message_size_limit to get much larger, you might need more RAM. At any rate, if you increase this, use 'top' to keep an eye on memory usage.

local transport disable/error message

local_transport Give an error message for local delivery attempts.

postconf -e "local_transport = error:no local mail delivery"

mydestination An empty mydestination tells Postfix this machine is not the final destination.

postconf -e "mydestination = "

local_recipient_maps An empty local_recipient_maps tells Postfix there are no local mailboxes.

postconf -e "local_recipient_maps = "

virtual alias/ virtual email

virtual_alias_maps Our spamfilter must be able to receive mail for postmaster@[]. Reportedly, some things actually expect this ability to exist. We will also allow mail to abuse@[]. Since we do not allow local mail delivery, mail addressed to our spamfilter IP address will get rejected with an error message. Setting up virtual_alias_maps allows email to these two accounts to be forwarded to an inside address. Make sure your Exchange server is set up to receive messages addressed to "root", "postmaster" and "abuse". Set up a reference to the virtual file:

postconf -e "virtual_alias_maps = hash:/etc/postfix/virtual"

Then edit the virtual file:

vi /etc/postfix/virtual

and add postmaster and admin in the format:

postmaster postmaster@example.com
abuse abuse@example.com

Save and exit the file, then create the binary file that Postfix will use:

postmap /etc/postfix/virtual

relay emails through outside

relayhost Generally speaking, if this machine is on an internal network (with no public IP address), you may need to configure 'relayhost'. If it is on the Internet serving as a gateway server, you would only configure 'relayhost' if you must relay your mail through some other server (like your ISP's), otherwise you would not. The relayhost is the email server you wish to use to send outbound email. The outbound email I'm talking about is the non-local mail, mail bound for domains other than ours, not the normal email that comes from outside the system and is bound for your internal mailboxes (we use /etc/postfix/transport to route those). At this time you are using a machine other than this one to send mail out to the Internet so you could place the IP address of that machine here (the brackets must be there). If preferred, you can use a host name instead of an IP address (keep the brackets, i.e. [gateway.example.com]). If this is blank, or not configured, then Postfix will use DNS to deliver outbound mail (which is the ideal configuration). It is best to not use relayhost, but if you do not, you should first have your reverse DNS record in place and of course your "A" record and "MX" record so other servers on the Internet will accept mail from this machine at this IP address. If these are not yet in place, it may be useful to temporarily configure relayhost. If you point relayhost to the Exchange server, the Exchange server (or other SMTP server) must be configured to allow our spamfilter to relay mail through it http://www.msexchange.org/pages/article.asp?id=54. You need this so bounces have a way out of the network. Read the notes above before you enter this:

postconf -e "relayhost = [666.666.666.666]"

You can optionally reconfigure your clients and other SMTP servers (including the Exchange server) to use our spamfilter for their outgoing mail. Keep in mind that if you use your spamfilter as your outbound SMTP server that your outbound mail will go through the same scanning process as your inbound mail (unless you prevent it - see http://www.freespamfilter.org/forum/viewtopic.php?t=283 and http://www200.pair.com/mecham/spam/bypassing.html). If you use this setting, make sure the relayhost you designate will accept email from this machine and THAT machine is not using THIS machine for ITS outgoing mail.

reject nonexistent users

relay_recipient_maps - We are going to build a table of every single user in every single domain that we accept mail for. This table will be used to reject mail that is addressed to nonexistent users in our domain(s). Don't freak out just yet. At this time we are only going to set up the structure of the table. Then you will come back to this after your spamfilter is functional and work on finding an automated process that can be used to populate the database. Or, if you have a manageable number of users, manually enter them. If this proves too daunting a task, we may have to rely on the Exchange server to do the 'user unknown' rejects. In some cases you might be able to use reject_unverified_recipient as an alternative. If you are in fact using Exchange, there are HOWTOs available that describe automating the process of building the relay_recipients table. It has been very common of late for spammers to launch 'dictionary attacks'; sending thousands of messages to a domain using fabricated user names. Our spamfilter will have to process each and every one of these unless you put your valid users in the relay_recipients table. Don't underestimate the importance of this and make sure you are not the only one in your organization who knows how to make changes to this file. Set up a reference to a file we will create to store the data:

postconf -e "relay_recipient_maps = hash:/etc/postfix/relay_recipients"

Then edit that file: vi /etc/postfix/relay_recipients

For the moment, we are going to accept mail for all users in our domain(s) so enter each domain you accept mail for in the format:

@example.com OK
@example2.com OK
@example3.com OK

Then create the binary file that Postfix will use:

postmap /etc/postfix/relay_recipients

The entries above are temporary. They are wildcards that allow mail to your domains. You MUST remove the entries above at some point in the near future and replace them with every single one of your valid recipients' email addresses. When you are ready to enter each user individually in the relay_recipients file, you would first remove (or comment out) the data above that allows mail to all users in the domain, and then list each user individually in the form:

user1@example.com OK
user2@example.com OK
user3@example.com OK

Actually, in this particular file the value "OK" listed after each user is not used for anything, but something must be there because a hash table requires a value after the key. Note that by eliminating root@example.com from this file, you can prevent users from the Internet from sending mail to root@example.com, but don't do this if some of your own servers need to use this machine to send mail to root. If you use Exchange, here are the HOWTOs I promised you. Even if you don't use Exchange, I found the information regarding file transfers useful. http://www2.origogeneris.com:4000/relay_recipients.html - http://www-personal.umich.edu/~malth/gaptuning/postfix/ - http://www.unixwiz.net/techtips/postfix-exchange-users.html - http://postfix.state-of-mind.de/patrick.koetter/mailrelay/

where to forward valid mail

transport_maps Tells Postfix where to look for a transport file. We use the transport file to tell Postfix where to forward valid mail addressed to our domain(s). Our file will be /etc/postfix/transport and we will set it up in similar fashion to relay_recipients. Create a reference to it in main.cf:

postconf -e "transport_maps = hash:/etc/postfix/transport"

Then edit it:

vi /etc/postfix/transport

Add 1 new line for each domain for which you will be handling mail, similar to the example below. The IP address is that of whatever server is the final destination of messages addressed to our domain(s) (our Exchange server). It does not matter where you place these items in the file, but I like to put them at the top.

example.com smtp:[666.666.666.666]
example2.com smtp:[666.666.666.666]
example3.com smtp:[666.666.666.666]

(DO include the brackets on these lines!) You can also use a FQDN hostname instead of an IP address (i.e. smtp:[exchange.example.com]).

Then create the binary file Postfix will use:

postmap /etc/postfix/transport

relay domain only for example.com

relay_domains What destination domains (and subdomains thereof) this system will relay mail for. You want to list here ONLY domains for which you are responsible for accepting mail. In addition to allowing mail to be relayed to these domains, this setting also infers that we do not relay mail to domains not listed here and therefore this is a critical anti-relay control setting. Separate the list with commas (technically, spaces also work).

postconf -e "relay_domains = example.com, example2.com, example3.com"

If you have many domains to list here, you would want to use a lookup table. An example would be to create a file "/etc/postfix/relay_domains" with the contents of the file in the format:

example.com 1
example2.com 1


example2.com OK

then set "relay_domains = hash:/etc/postfix/relay_domains" in main.cf, then "postmap /etc/postfix/relay_domains" and "postfix reload" at the command prompt. See http://www.postfix.org/postconf.5.html#relay_domains for details.

recipient delimiter

recipient_delimiter If your current SMTP/POP3/IMAP server is configured to use address extensions (for example user+foo@example.com) then recipient_delimiter should be set to match the delimiter you are currently using to separate the user name from the address extension. Amavisd-new also uses $recipient_delimiter and this setting needs to match the Postfix setting. This has nothing to do with the comma you are using to separate multiple people you send email to (user1@example.com, user2@example.com, user3@example.com) using your email client (MUA). Typical settings - Choose one I Don't use recipient delimiters: This is a default

postconf -e "recipient_delimiter = "

I currently use the plus sign:

postconf -e "recipient_delimiter = +"

I currently use the minus sign:

postconf -e "recipient_delimiter = -"

If (and only if) the IP address you present to the world is not the IP address of your spamfilter (you are configured to run behind a NAT firewall or a proxy server) please add these two lines to main.cf, then you must uncomment and configure proxy_interfaces ( represents the public IP address):

proxy external address

# Specify your NAT/proxy EXTERNAL address here. #proxy_interfaces =

address rewriting

Address rewriting. When using a content_filter like amavisd-new, because mail is sent to Postfix twice, address rewriting takes place twice unless we disable it either before amavisd-new or after amavisd-new has processed a message. Our virtual file is one example of a table that rewrites addresses. It is up to you to decide whether you want amavisd-new to see the original address, or the rewritten address.

In master.cf you can disable address rewriting before amavisd-new by setting:

smtp inet n - - - - smtpd

Be careful, there are two lines that look similar. You are looking for smtpd on the right hand side. To instead disable address rewriting when amavisd-new returns (non discarded) messages to Postfix, you would edit the current receive_override_options override on the reinjection port ( For example, if we now have: inet n - - - - smtpd [...lots of overrides are here...]

You would change this to: inet n - - - - smtpd [...lots of overrides are here...]

vi /etc/postfix/master.cf and edit one or the other.


Postfix Anti-Spam settings

Index ****************************************************** Preliminary Notes:

When a client (a computer trying to send us mail) connects to Postfix and begins a communication session, Postfix records information about that session. Prior to the point where Postfix accepts mail from that session for delivery, we have the option of evaluating the session and rejecting the mail by setting some restrictions in main.cf. This link illustrates what happens during a typical SMTP session: http://helpdesk.islandnet.com/pep/smtp.php. The restrictions below help ward off some spam and prevent our system from becoming an open relay. These restrictions cause some mail to be rejected by Postfix right at the "front door". This will save system resources because the mail will not enter our system and therefore will not be scanned by amavisd-new (and subsequently by SpamAssassin). This is good and bad. It saves system resources, but it also doesn't let you see the rejected mail. All you will see is a log entry or two from Postfix saying essentially "Hey, a mail server named "xxxxxxxx" at IP address X.X.X.X tried to send some mail in, but it broke rule XYZ, so I rejected it". Now this could have been spam (spammers often intentionally don't follow RFCs in order to accomplish their goals) but if it was a "legitimate" mail, say from a customer whose IT Department has simply misconfigured their mail server (it happens), you could have some ruffled feathers to deal with.

If you want to allow ALL mail addressed to us to come in the front door, and therefore allow amavisd-new/SpamAssassin to handle all spam control within the system, you would need to modify a couple of the settings below. I personally find a combination of Postfix and SpamAassassin anti-spam control to be best. At the very least you need to insure you do not disable the built in default anti-relay control in Postfix (smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination).

The configuration below is actually very conservative, allowing most email to come in the front door so amavisd-new and SpamAssassin have their shot at it. For me it (safely) rejects about 35% of the email bound for my users, so I think these settings are quite valuable. I recommend this approach to start. Adding additional restrictions will increase the likelihood of rejecting valid email from improperly configured computers. If you decide to add/remove permissions/restrictions in the future, do so one at a time and give yourself ample time to evaluate the effect of the change. I strongly suggest you actually have a good understanding of how these restrictions work before you make changes to the entries below. Among other things, getting this stuff wrong could reject legitimate mail and/or cause us to become an open relay. Note that restrictions don't always restrict, some also permit.

If you want to gain a better understanding of these settings, good resources are http://jimsun.linxnet.com/misc/postfix-anti-UCE.txt, http://www.postfix.org/SMTPD_ACCESS_README.html, http://www.securitysage.com/antispam/, the somewhat dated (2001) http://www.mengwong.com/misc/postfix-uce-guide.txt, and this excellent book. You will note I only use a couple of the same settings as these, so this configuration is no where near as restrictive. Keep in mind that SpamAssassin and amavisd-new will come into the picture in a bit, and will provide us with much more flexible and configurable options to recognize and manipulate spam.

smtpd hello required

smtpd_helo_required: Make any connecting mail server do a proper smtp "handshake" and announce its name. Internet RFCs require this, so we do too.

postconf -e "smtpd_helo_required = yes"

Preface: Postfix' restriction stages are as follows, and are processed in the following order:

restriction stages


sender restrictions

We are only going to place entries in the last three restriction stages. Restriction stages are processed in this order regardless of the order listed in main.cf

smtpd_sender_restrictions: This restriction stage restricts what sender addresses this system accepts in MAIL FROM: commands (the envelope sender). We will place three tests (restrictions) in this restriction stage.

A restriction stage holds a list of restrictions (tests). Typically, tests evaluate to either DUNNO, REJECT, or OK. DUNNO means "I don't know what to do, let the next test decide". REJECT simply rejects the mail. OK means no more tests are performed in this restriction stage, tests continue with the next stage (if any). Reject_* type tests typically evaluate to REJECT or DUNNO. Permit_* type tests typically evaluate to OK or DUNNO, and check_*_access type tests can perform a variety of actions. The illustration shows the basic logic.

         SMTP session
restriction stage-------------

  test ---------------REJECT->
   |   \
   |    DUNNO
   |     \ 
   |      V
   |   next test------REJECT->
   |      |   \
   OK     OK   DUNNO
   |      |     \ 
   |      |      V
   V      V
next restriction stage-------

1) check_sender_access See http://www.postfix.org/access.5.html. Here we ask Postfix to compare the envelope sender to entries in an /etc/postfix/sender_access database and act upon those entries if a match is found. We also define what action is taken there (OK, DUNNO, REJECT etc.) on a sender by sender basis. If the sender is not listed in the file, the test evaluates to DUNNO, and the next test is performed. I will provide examples a little later. One use of this file is to place a list of senders (email addresses, domains, network addresses etc.) from which we wish to not receive mail (blacklist them). We will also have the ability to blacklist senders in amavisd-new and SpamAssassin but it will save resources if we blacklist them here. We will also use this file to allow specific senders to bypass the next two tests in this restriction stage. If we give them an OK here, no more tests are performed in this restriction stage, the tests continue in the next restriction stage (smtpd_recipient_restrictions). Note that if we were to place this setting in the smtpd_recipient_restrictions restriction stage before the reject_unauth_destination test, and we were to give someone the OK there, the reject_unauth_destination test located there would be bypassed. This would be bad because anyone we gave the OK to would then be able to use our server as an open relay. Access restrictions are evaluated in the same order we list them, and if a match is found it will influence how (whether) further restrictions are evaluated.

2) reject_non_fqdn_sender Reject when the envelope sender mail address is not in the proper format. Remember, the "envelope sender" is what the sending mail server gives in the "MAIL FROM:" line during the SMTP session, not the header "From:" line. "Joe" is not allowed to send us mail (because we can't reply to "Joe") but "Joe@example.com" is at the very least an email address. If the sender does not get rejected at this point, this test evaluates to "DUNNO".

3) reject_unknown_sender_domain Reject when the envelope sender's domain part of the mail address has no DNS "A" or "MX" record at all. This setting kicks about 35% of the mail coming in my mail server. It is common for spammers to use a bogus domain name so they don't have to deal with the backlash of rejected mail. It is also important for us not to fill up our queue with Bounce notices that can never be delivered due to the fact that the sender's domain does not even exist. If the sender's domain has an "A" or "MX" record, this test will also evaluate to "DUNNO". On occasion, you will see in a report that someone you wish to receive mail from has been rejected by this setting. One possible cause of this is when legitimate senders deliberately use bogus domain names so you will not reply to them. This is where the sender access list comes in handy. You can give them an OK there, and this test will be bypassed.

postconf -e "smtpd_sender_restrictions = check_sender_access hash:/etc/postfix/sender_access, reject_non_fqdn_sender, reject_unknown_sender_domain"

recipient restrictions

smtpd_recipient_restrictions: The access restrictions that the Postfix SMTP server applies in the context of the RCPT TO: command. This refers to the "envelope recipient" which is what the client gave in the "RCPT TO:" line during the SMTP session, not the header "To:" line. smtpd_recipient_restrictions is another restriction stage that holds a list of specific restrictions. Other restriction stages that are evaluated prior to smtpd_recipient_restrictions are smtpd_client_restrictions, smtpd_helo_restrictions and smtpd_sender_restrictions (in that order). Restrictions that would normally go in these prior restriction stages can alternately be placed in smtpd_recipient_restrictions. Therefore, some people prefer to place all the smtpd_*_restrictions that would normally go in prior restriction stages into smtpd_recipient_restrictions (in the proper order) and leave the prior stages unconfigured (empty). In our case it is safer to use smtpd_sender_restrictions and smtpd_recipient_restrictions. Let's look at those specific restrictions (tests) we place in smtpd_recipient_restrictions:

1) permit_mynetworks Allows machines listed in "mynetworks" to skip the rest of the tests in this restriction stage (permit = OK). In other words, it exits this stage and is tested in the next stage (smtpd_data_restrictions). Because permit_mynetworks is placed in front of reject_unauth_destination, this means machines in $mynetworks are allowed to relay mail to any domain. Without this, we would only be able to send mail to our own domain(s). If the IP address of the sender is not listed in $mynetworks, the test evaluates to "DUNNO" and continues on to the next test (reject_unauth_destination).

2) reject_unauth_destination This, along with permit_mynetworks is used for relay control. This setting, in essence, means that mail bound for any domain that we have not configured our machine to accept mail for will be rejected. In our case Postfix will use the relay_domains setting (or table) that we configured earlier to determine what domains those are. See http://www.postfix.org/postconf.5.html#reject_unauth_destination for additional details. If the domain is listed in relay_domains, this test evaluates to "DUNNO" and the session is allowed to go on to the next test (if any). Just like "mynetworks", this setting is extremely critical. By placing permit_mynetworks directly ahead of reject_unauth_destination, we are assured that we can send mail to domains other than ours, but we will only accept mail addressed to us from computers outside our network, thus permit_mynetworks and reject_unauth_destination work as a team.

3) reject_unauth_pipelining Rejects bulk mailers that attempt to use pipelining to speed delivery, without checking if it is supported first (non-RFC, common among spammers).

postconf -e "smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination, reject_unauth_pipelining"

smtp data restrictions optional

smtpd_data_restrictions: Optional access restrictions that the Postfix SMTP server applies in the context of the SMTP DATA: command. Like smtpd_recipient_restrictions, this is a restriction stage.

1) reject_unauth_pipelining I repeat this setting in smtpd_data_restrictions as it is not always effective when placed in smtpd_recipient_restrictions. I include it in smtpd_recipient_restrictions as I like to place it prior to any policy servers (discussed in a separate document I show you later). Note that there are only a couple of restrictions that make good use of smtpd_data_restrictions.

postconf -e "smtpd_data_restrictions = reject_unauth_pipelining"

content filtering controls

Postfix content filtering control files: http://www.postfix.org/header_checks.5.html /etc/postfix/header_checks and /etc/postfix/body_checks These files will list certain "strings" of text, and tell Postfix what to do with mail if it encounters these strings in email headers or the body of the message. Sample files are already created for us, with comments explaining what to put in them. You can edit them at your leisure. Note that these files require the use of "regular expression format". "regexp" is something you'll want to learn about in order to live in the *nix world. Get a book or research it on the Net sometime. For an example of an elaborate header_checks file from someone with an attitude, take a look at http://www.geekounet.org/filters/header_checks. But don't blindly follow this, it's only an example! Here is an example of a body_checks file: http://www.securitysage.com/files/body_checks. It would be worth your while to check out http://www.securitysage.com/guides/postfix_uce.html when you have a leisure moment. Specifically http://www.securitysage.com/antispam/hedchek.html and http://www.securitysage.com/antispam/bodchek.html. I recommend against making a large number of changes to any part of Postfix without giving yourself plenty of time to evaluate the effects. Like a turtle, go slow, live long.

header checks

Another note about header_checks. Some people wish to get rid of the "Received: from localhost" header by making a rule something like: /^Received: from localhost \(localhost\.localdomain \[127\.0\.0\.1\]\)/ IGNORE but get frustrated when it does not seem to work. The reason would be because this header is written after the mail has passed from amavisd-new, but in master.cf we have disabled header_checks and body_checks when mail is returned to Postfix with the override:

so you would have to remove "no_header_body_checks" if you want to work on headers written after the message has left amavisd-new. You can remove the other amavisd-new related header by setting "$insert_received_line = 0;" in amavisd.conf. The downside would be all your costly header_checks and body_checks will be performed again.

header_checks: Optional:

postconf -e "header_checks = pcre:/etc/postfix/header_checks"

Note that we do not have to 'postmap' pcre type tables. They remain plain text and Postfix uses them "as is".

body checks

body_checks: Optional:

postconf -e "body_checks = pcre:/etc/postfix/body_checks"

Keep in mind that you could also configure mime_header_checks and nested_header_checks along with header_checks and body_checks. Note that enabling content filtering in Postfix (we are using header_checks and body_checks) can have a significant impact on performance in Postfix. If later you find that you have not had occasion to place any entries into these files, you should comment them out in main.cf.

content filter

content_filter: Here's where we tell Postfix to use amavisd-new. http://www.postfix.org/FILTER_README.html

postconf -e "content_filter = smtp-amavis:[]:10024"

allow sender, no fileter nor checks

/etc/postfix/sender_access http://www.postfix.org/access.5.html We referenced this file in smtpd_sender_restrictions. We use this file to check the sender right at the front door. In this file, we'll list certain senders/domains/IPaddress ranges for special handling. Below are bogus examples, create your own as you see fit. Please read /etc/postfix/sender_access for more information. Although you could use this file for various purposes, considering the way we have set this up in smtpd_sender_restrictions, I suggest using it to either blacklist senders, or allow certain senders to bypass the remaining tests in smtpd_sender_restrictions.

vi /etc/postfix/sender_access

#Example sender access map file

makeabuck@mlm.tld 550 No MLM thanks
allspam.tld 550 Spam is not accepted here
badguy.net REJECT
justaspamminfool@allspamallthetime.com REJECT
newsletter-fake-domain.com OK
my-bogus-test-domain.com OK

Since this is a hash table, you need to postmap it as usual:

postmap /etc/postfix/sender_access

Let's take a look at our changes:

vi /etc/postfix/main.cf

Check the contents of the file for errors and repair if needed. You will probably want to edit relay_domains and mynetworks.

postfix start

check postfix responses

Check that Postfix responds:

telnet 25

You should see:

220 sfa.example.com ESMTP Postfix (Debian/GNU)

hit [enter] a few times; then type: quit to exit

If it does not reply in this manner, open another terminal window and stop Postfix (postfix stop). Make sure you ran newaliases and all the postmap commands above. Check all the settings in main.cf and master.cf. There is a nice paper on troubleshooting Postfix at http://www.postfix-book.com/debugging.html but keep in mind our system is not ready to relay mail at this point (it will end up in the queue because we have not yet configured amavisd-new).

Any time you make changes to master.cf or main.cf or to data tables, most (not all) of the time, it is required that you to reload Postfix.

postfix reload

Now that we have a basic Postfix configuration, http://www.postfix.org/STANDARD_CONFIGURATION_README.html#firewall and http://www.postfix.org/BASIC_CONFIGURATION_README.html are good places to gain a better understanding of some of the settings we used and at this point these READMEs will make more sense. I am personally using this box on an internal network so I have chosen to omit some of the Postfix configuration parameters that may apply to a system that is on the Internet, but Postfix should function fine the way we have it set up so far even if it is on the Internet. Once our system is fully configured you may wish to use the examples in these READMEs to enhance the settings we have made thus far to better suit your needs. Don't send mail through the system just yet, we need to configure amavisd-new first.

By default, our Postfix runs chrooted. If you don't know what that means, it will not matter much at this point. I leave it to you to research what 'chroot' means at some later time. Some of the system files that Postfix needs to run properly were copied to Postfix's chroot jail (/var/spool/postfix) during installation. On occasion, the original files will get modified, and Postfix will complain that the copy it has is not the same as the original. When this happens, you can manually copy the file(s) postfix has complained about to the chroot jail, or we can simply run a script that is supplied with the Postfix source code (called LINUX2) that will once again copy all the files that Postfix needs to where it needs them.

Quick lesson: To change to the Postfix directory shown below, you could type cd p then hit the [tab] key and the bash shell will fill the remainder in with the first unambiguous item. If there is more than one item, you can hit the [tab] key twice and it will list all the available items. For example, the second line below could be entered as cd p[tab] e[tab] c[tab][enter]

cd /usr/local/src

This next line may be edited for a different version of postfix: cd postfix-2.3.3/examples/chroot-setup

postfix start chmod +x LINUX2 cp LINUX2 /usr/bin LINUX2 cd

postfix check

You can check if Postfix is happy:

postfix check

This makes the LINUX2 script executable, copies it to a directory in our path, Then executes it.

At this point, if this server is going to be on the Internet (as opposed to residing on an internal network) you can greatly decrease the load on the server by increasing the amount of mail that is rejected at the front door. You may choose to continue on without reading it right now, and consider using that document a little later, as it is optional (but highly recommended). Additional anti-UCE settings for our Debian Anti-Spam Anti-Virus Gateway Email Server

Configuring amavisd-new

****************************************************** Configuring amavisd-new: Index ****************************************************** Since in new debian version of amavisd-new there is a different layout of configuration we will do the following.

First, make a backup of the amavisd-new config files:

cp -r /etc/amavisd/conf.d /etc/amavisd/conf.d.original

General note. The settings used here are what might be used at small business. A business where the users trust the administrator(s) to make choices for them. In more complex systems, individuals will want their own personal settings. I do not cover that scenario in this document. Suffice it to say that if you need to provide individual settings for a large number of users, the most efficient way to do this would be to use LDAP or SQL to store those settings (dynamic tables). You would need to read the amavisd-new documentation and have some knowledge of LDAP or SQL. You can however provide individual settings to a small number of users by using static tables directly in amavisd.conf, or in plain text files read into amavisd-new via the read_hash() function. There are examples in amavisd.conf. If you use static tables, it is necessary to stop and start amavisd-new after each change.

Next, we'll edit this file, but first let me just mention that this file is a very important part of configuration control in your spam system. There are many settings in here. I won't cover all of them by any means. This file is an abbreviated version of one of those heavily commented config files that some hate, others love. I recommend you return and spend some time reading /etc/amavis/amavisd.conf-sample after this system is all set up, to learn more about just what you can do with amavisd-new. We are going to start at the top of the file and work our way down. Remember, in vi you can search for a string by hitting [Esc], a slash, the text to search for, and optionally a lower case 'n' to find the next occurrence. Once you find what you want, don't forget to use 'i' to start editing. I personally find it much easier to edit this particular file using the WinSCP editor (select the file, hit F4 to edit).

Either: vi /etc/amavis/conf.d/50-user

or use the WinSCP editor to edit this file.

If the following lines are missing in 50-user please add them in. Do not forget the colons at the end.

Insure the amavis user and group are set like so:

$daemon_user = 'amavis';
$daemon_group = 'amavis';


Nothing to do here, just make sure you have followed the steps when we setup the hostname.


Your domain name is stored in file /etc/mailname double check it is there:

cat /etc/mailname

If it is not add it in

vi /etc/mailname

type your domain name:


and change to reflect the actual name of our domain.

Next, locate this next line:

@local_domains_acl = ( [".$mydomain"] );

Comment out that line, then add a new one just like it with all your domains listed in it. Like this:

@local_domains_acl = ( [ ".$mydomain", '.example2.com', '.example3.com' ] );

Or like this:

@local_domains_acl = ( [qw( .example.com .example2.com .example3.com )] );

The periods in front of the domains are wildcards for subdomains (or hosts). Don't forget the semi-colon at the end. Note that in Perl, single quotes and double quotes work differently from each other. We need this in order for all our domains to see the SpamAssassin scores in the header of each message. If you have a large number of domains to list, read the instructions in amavisd.conf-sample on creating a Perl hash lookup table. The reason we need our domains listed here is explained in http://www.ijs.si/software/amavisd/#faq-spam


spamassassin settings

Let's move on to SpamAssassin settings. Amavisd-new calls SpamAssasssin like a sub-routine. SpamAssassin picks up all settings in local.cf, but modified mail as prepared by SpamAssassin is not used, amavisd-new does its own modifications to the original mail. These settings are part of what determines what amavisd-new does with the mail and may include rewriting of the Subject: line, addition of the X-Spam-* lines in the headers and possibly directing amavisd-new to take other action with the mail.


$sa_tag_level_deflt = 2.0;


$sa_tag_level_deflt = undef;

This will insure all mail addressed to domains in @local_domains will get a spam score in the header, spam or not.


$sa_tag2_level_deflt = 6.31;


$sa_tag2_level_deflt = 5.0;

This low number is assuming your email clients do not automatically discard spam. Set this to 8.0 or higher if they do.

The Subject line will be prepended with "***Spam***" for any mail that scores above $sa_tag2_level_deflt and is passed to a recipient.


$sa_kill_level_deflt = 6.31;


$sa_kill_level_deflt = 8.0;

On our system, this will trigger the spam to be quarantined if it scores 8.0 or higher. If you plan on deleting the spam, set this at 12.0 or higher. If you only want spam tagged and sent to the recipients (not quarantined at all), set this at 9999 (this would be for ISPs and large companies that configure the MUAs to further process spam). To better understand these and other settings, see http://www200.pair.com/mecham/spam/amavisd-settings.html. I believe these are good starting points. The comments provided in the file give some clues what these settings mean. See amavisd.conf-sample for more clues. With a kill level of 8.0 you can expect a fair amount of spam to slip through this system and into your users' mailboxes initially, but it will get better as time goes on. The Bayes filter included with SpamAssassin will not kick in until it has processed at least 200 pieces of "ham" or "non-spam". The length of time it takes to do this completely depends on how many email messages this system processes per day. Mine took about a week to find 200 legitimate email messages to work with. It does it all automatically but later I will explain how to help it along. Once the Bayes filter kicks in, the kill level of 8.0 will be just about right. It will be on the conservative side. Wait a few weeks and keep an eye on the spam. If you choose a kill_level score lower than the one I suggest, the more effort there is on your part to find false positives because there will be more of them in the spambin. Speaking of the Bayes database: the amavisd-new package maintainers were kind enough to write a couple of scripts that keep the database up to date and clean. They run as cron jobs and consist of /etc/cron.d/amavisd-new and /etc/cron.daily/amavisd-new. Note that when these cron jobs are running, the Bayes files will at times be inaccessible. If you happen to see in a log file that SpamAssassin has timed out, this could be one possible reason.

Now find:

$virus_admin = "postmaster\@$mydomain";

The default is fine, but you may wish to change it. Now add a line for banned file notifications:

$banned_admin = "postmaster\@$mydomain";

mail notification

When we do send a virus or banned file notification, this is whom the notification will go to. Banned attachments are treated much like viruses, and right out of the box, amavisd-new will want to quarantine emails that contain banned attachments. Initially, the only banned attachments it is configured to quarantine are ones with double extensions, i.e. "filename.gif.pif" and a few major risks like ".exe".

Next, locate this section:

$mailfrom_notify_admin     = "virusalert\@$mydomain";
$mailfrom_notify_recip     = "virusalert\@$mydomain";
$mailfrom_notify_spamadmin = "spam.police\@$mydomain";

change it, or if it is not there, add it:

$mailfrom_notify_admin     = "postmaster\@$mydomain";
$mailfrom_notify_recip     = "postmaster\@$mydomain";
$mailfrom_notify_spamadmin = "postmaster\@$mydomain";

Just below this, remove the '#' to uncomment this line: # $hdrfrom_notify_sender = "amavisd-new <postmaster\@$mydomain>";

For a discussion of these settings, see http://marc.theaimsgroup.com/?l=amavis-user&m=111938103904411&w=2

Optional: $sa_spam_subject_tag = '***SPAM*** '; to $sa_spam_subject_tag = 'Spam> '; The longer version simply takes up too much real estate on the subject line, but it is very visable when looking at 100 of emails. You choose.


Next, locate the line that looks like this:

$virus_quarantine_to = 'virus-quarantine';

I suggest you do one of three things here. You can leave this alone, and viruses will be quarantined on the spamfilter box, or you can set this to:

$virus_quarantine_to = undef;

and provided we configure a virus scanner, all caught viruses will disappear, or you can send caught viruses to a regular mailbox:

$virus_quarantine_to = "virii\@$mydomain";

You can choose to use "spambin" for the quarantine area for all spam, viruses and email with banned attachments, but I recommend you create separate mailboxes for each. If you choose to store quarantined viruses (or any other type of quarantined mail) on your spamfilter box, keep in mind that you will have to eventually delete them, and on rare occasions you may need to forward a sample to an email address. These files will be stored in the /var/lib/amavis/virusmails directory. You can use a program supplied with the amavisd-new source code called 'amavisd-release' to send items in the quarantine to an email address if needed. Read the amavisd-release file itself for more details. You will have to make changes to amavisd.conf and make this program executable before you can use it. If you send viruses to a regular mailbox, make sure the desktop virus protection is up to date on the client that retrieves these messages, and remember - don't open attachments with viruses in them!

Next, locate the $banned_quarantine_to line and configure these three lines in this manner: $banned_quarantine_to = "banned\@$mydomain"; $bad_header_quarantine_to = "banned\@$mydomain"; $spam_quarantine_to = "spambin\@$mydomain";

Make sure you have mailboxes for these two addresses on a destination server. This is where you will review quarantined email, and if ham is found, will forward the ham to the proper recipient.

banned files

Locate this block inside the $banned_filename_re = new_RE section:

# qr'.\.(exe|vbs|pif|scr|cpl|bat|cmd|com)$'i, # banned extension - basic+cmd # qr'.\.(ade|adp|app|bas|bat|chm|cmd|com|cpl|crt|emf|exe|fxp|grp|hlp|hta| # inf|ins|isp|js|jse|lnk|mda|mdb|mde|mdw|mdt|mdz|msc|msi|msp|mst| # ops|pcd|pif|prg|reg|scr|sct|shb|shs|vb|vbe|vbs| # wmf|wsc|wsf|wsh)$'ix, # banned ext - long

If you would like to greatly extend the types of attachments amavisd-new bans, you might want to comment out, and uncomment some lines like so:

# qr'.\.(exe|vbs|pif|scr|cpl)$'i, # banned extension - basic # qr'.\.(exe|vbs|pif|scr|cpl|bat|cmd|com)$'i, # banned extension - basic+cmd

Just edit out the attachment types you would like to receive or edit in any others you would like to ban. Each vertical bar means "or". I would add bin|drv|mht|ocx|ovl| If you receive mail from people using Outlook in Rich Text mode, make sure you don't block |tnef When an email that has one of these attachments comes into the system, the entire message gets placed in quarantine and the sender and postmaster get notified. Using this feature of amavisd-new goes a very long way toward preventing email borne viruses from entering your network. This method should not be your only line of defense however, just another tool in your arsenal.

Next, locate the # ENVELOPE SENDER SOFT-WHITELISTING / SOFT-BLACKLISTING section. Spend a moment to read through the comments at the beginning of this section simply to make you aware of what is there, and what it is used for. Negative scores for sender addresses mean "make their mail appear less spammy" and positive scores mean "make their mail look more spammy".


recipient delimiter


Next, locate # $recipient_delimiter. You set recipient_delimiter in Postfix and the setting in this file needs to be set similarly. This is typically set to one of these three options:

$recipient_delimiter = '';  # No recipient delimiter (this is the default)


$recipient_delimiter = '+';


$recipient_delimiter = '-';

final spam/virus destiny

The next line I would like to change begins with:

$final_spam_destiny = D_BOUNCE;

Change this to:

$final_spam_destiny = D_DISCARD;

This does not actually discard mail; the spam still ends up in our quarantine. The difference between D_BOUNCE and D_DISCARD is D_DISCARD will not send a bounce notice to the spammer for a piece of mail that is marked as spam. Unlike spam, we may want to notify the sender of a banned attachment that their mail was not delivered. We usually don't want to notify senders of viruses (because the sender is probably spoofed). This is a personal choice; I don't want my queue to be full of bounce notices that can't be delivered to spammers. From their perspective, the spam was successfully sent. If we set our SpamAssassin kill level high enough (12 at the very least), D_DISCARD CAN be used to actually discard mail. To do so, you could either set: $spam_quarantine_to = undef; and the email with a SpamAssassin kill score of 12 or higher would evaporate into thin air, or you could configure $sa_quarantine_cutoff_level. But don't do this; at least not yet. Setting $spam_quarantine_to = undef; essentially means "we don't have a spam quarantine area so I guess I have to just dump the mail". This is something you probably should not implement at first; at least not if you enjoy being employed. If you decide to do this, I suggest you wait a month or so to get a feel for the system (and let the Bayes database initialize). You can eliminate about 90% of the email that ends up in the "spambin" by using this suggestion.

If you have a powerful machine with sufficient RAM (512MB or more), at some time in the future you may want to experiment with increasing the number child processes that amavisd-new spawns. More child processes means that amavisd-new can process more mail in a given amount of time (up to a practical limit). See http://www.ijs.si/software/amavisd/amavisd-new-magdeburg-20050519.pdf. If you configure your system to use more instances of amavisd-new, allocate at least 40MB for each additional instance. It you wanted to double the number of child processes from 2 to 4, you would edit 50-user and change:

$max_servers = 2;


$max_servers = 4;

Then edit /etc/postfix/master.cf and change:

smtp-amavis unix - - - - 2 smtp


smtp-amavis unix - - - - 4 smtp

Amavisd-new will be the biggest bottleneck in the system. On a busy server you will probably want 2GB RAM so you can accomodate somewhere around 15 $max_servers.

Our system will log to both /var/log/mail.log and /var/log/mail.info. We don't really need the log duplicated to /var/log/mail.info: Optionally disable logging to /var/log/mail.info: vi /etc/syslog.conf

and comment out the mail.info line, like so:

#mail.info -/var/log/mail.info

We can wait for the next reboot for this to take effect.

There are files that act as templates (that can be modified) that are used as the basis for the text used in email notifications. Normally these templates are stored inside the amavisd-new file itself, but it is possible to copy this text into external files, and then place a setting in amavisd.conf that uses these external files. The typical Debian installation is configured to use these external files but I have commented out the setting in our custom amavisd.conf. If you don't plan on customizing any of the templates, you can simply leave the external files disabled: Optional:

If you would like to enable the external template files so you may customize them in the future (English only): vi /etc/amavis/30-template-localization

and uncomment the line: # read_l10n_templates('en_US', '/etc/amavis');

backup copy

Save the file with [Esc]:wq and exit vi. Then make a backup:

cp /etc/amavis/conf.d /etc/amavis/conf.d.19dec06

I have a habit of using the date for my backups.

debug amavis

Let's give amavisd-new a little test run (amavisd-new must be stopped before running it in debug mode):

amavisd-new stop
amavisd-new debug

After just a few moments, if you have something misconfigured; amavisd-new will tell you. At this point don't worry about the razor2 error if you get it. If you have an error in /etc/amavis/amavisd.conf, it will give you a line number and a brief explanation. Fix anything wrong. This will mean reading closely any error messages, and possibly reading the files in /usr/local/src/amavisd-new-2.4.4. There are friends at the AMaViS mailing lists waiting to help. https://lists.sourceforge.net/lists/listinfo/amavis-user. If everything is OK, and it should be, you will see a lot of lines that look like text log entries (exactly what debug mode does - logs to the screen), and near the bottom you will see "Parent ready for children". You can ignore the lines above this that talk about things like "INFO: no optional modules:" and "No decoder for" and "Cache not available", these are not errors, they are simply informational. FYI, each time amavisd-new starts up normally on your box, all these lines will be recorded in the system log files. Use the [Ctrl]+c key combination to exit (kill) amavisd-new debug.

If you are interested (and I realize this link may unnecessarily give you information overload at this point), there is one issue with quarantining mail in the manner I suggest above. The author of amavisd-new (Mark Martinec) suggests using Plus Addressing as an alternative. http://www200.pair.com/mecham/spam/plusquarantine.html

Pyzor Razor Spamassassin


****************************************************** Pyzor, Razor and SpamAssassin configuration: Index ****************************************************** Pyzor configuration. Here we supply the IP address of the Pyzor server to Pyzor (for both the 'root' and 'amavis' users). This will create a .pyzor directory in both user's home directories, and place the server's IP address in a 'servers' file therein:

pyzor discover
su amavis -c 'pyzor discover'

Test the pyzor server for a response:

pyzor ping
su amavis -c 'pyzor ping'

More than likely, you will get TimeoutError:. I recommend using a server other than the one 'pyzor discover' gives us:

echo "" > /var/lib/amavis/.pyzor/servers
echo "" > /root/.pyzor/servers

Then test again:

su amavis -c 'pyzor ping'

If in the future the IP address of the server changes, you will need to run the two 'pyzor discover' commands again. I suggest you subscribe to http://lists.sourceforge.net/lists/listinfo/pyzor-announce.

These commands make the Pyzor files world readable and sets the IP address of a Pyzor server. You can find the address of the current Pyzor server here.


You will need a sample spam to feed to spamassassin:

cd /root
wget http://www200.pair.com/mecham/spam/sample-spam.txt

This next section gets Razor2 up and running and copies its files where both root and amavis expect to find them. If you were to run amavisd-new -d config debug-sa you would notice that amavis expects to find programs and configuration files in certain places. If you were to run spamassassin -D config </root/sample-spam.txt as root you would notice that root expects to find the same things, but it expects to find some of them somewhere other than where the amavis user expects. SpamAssassin is designed to enable each user to have their own settings and data. This section will make both users happy, and the reason we want to do this is because if we are debugging SpamAssassin or Razor or Pyzor or DCC, we want to be able to do so with spamassassin -D </root/sample-spam.txt rather than amavisd-new debug-sa because we don't want to shut amavisd-new down every time we need to debug one of those programs. A better way to debug SpamAssassin is to run the program as the amavis user like so:

debug spamassassin

su amavis -c 'spamassassin -D </root/sample-spam.txt'

spamassassin -D </root/sample-spam.txt

Just to make sure SpamAssassin is alive. Running this may create some files also. We run this the first time as root. If Pyzor is working, you will see "Pyzor: got response:" Pyzor queries a Pyzor server in much the same way your computer queries a DNS server. The only practical difference is the port number that is used. DNS uses port udp 53 and Pyzor uses port udp 24441. If Pyzor is not working, you most likely have a firewall in front of this machine that is blocking the response. It is also possible the Pyzor server is not working. Refer back to the Pyzor configuration section and try the other server listed there. If you need to open a hole in a firewall or router, configure it just as you would DNS port 53, but substitute port 24441. While you are at it, do the same for port 6277. DCC will use port udp 6277. Notice in our firewall settings above that these 2 ports are configured just like DNS. Razor will need the ability to ping the outside world and outgoing tcp port 2703 must not be blocked. As far as DCC, Razor and Pyzor go, try them before you start messing with your Internet firewall. I have my spamfilter behind a screening router, a hardware firewall, and software NAT box firewall and none of them required reconfiguration for these programs to work.

http://www.dcc-servers.net/dcc/firewall.html gives an example of a Cisco router access list entry. Keep in mind we are not running a DCC server. Also http://www.oddquad.org/linux/anti-spam.html#providefirewallaccess will give you some idea of what we are after.

spamassassin for amavis user

We are going to make a backup of the original installation files then copy some of them to where the amavis user expects to find them.

cp -ir /root/.spamassassin /root/.spamassassin-backup

Please answer 'n' to "overwrite?":

cp -ir /root/.spamassassin /var/lib/amavis

We are going to make a symbolic link, so we only have to deal with one user_prefs file for both the root and amavis users.

rm /root/.spamassassin/user_prefs
ln -s /var/lib/amavis/.spamassassin/user_prefs /root/.spamassassin/user_prefs

If you run sa-learn --force-expire or spamassassin --lint -D or other spamassassin commands from the root account, SpamAssassin may change the owner of the Bayes files to 'root'. If it does, amavis will no longer be able to read those files. You would need to run chown -R amavis:amavis /var/lib/amavis to regain ownership. In general, if you do any spamassassin maintenance from the command prompt as root, the best thing to do is run

chown -R amavis:amavis /var/lib/amavis

afterwards; just to make sure. You can avoid these problems by remembering to run spamassassin commands as the amavis user. For example

su amavis -c 'sa-learn --sync --force-expire'

This next section configures Razor; sets the elusive "razorhome" and makes both root and amavis happy in their attempts to figure out "where in the heck are the Razor2 configuration files"?

rm /etc/razor/razor-agent.conf
razor-admin -create
razor-admin -create
razor-admin -register

If you get an error, you may need to run the 'razor-admin register' command more than once. Don't worry about it if /etc/razor/razor-agent.conf does not exist. Now edit root's razor configuration file:

vi /root/.razor/razor-agent.conf

and change the line:

debuglevel = 3


debuglevel = 0

Obviously -zero- not -oh-; Save and exit the file. OK, now copy root's .razor directory and files to the amavis user's home directory:

cp -r /root/.razor /var/lib/amavis
chown -R amavis:amavis /var/lib/amavis

We copied root's Razor stuff to where the amavis user expects to find it, so now we have a razorhome for both root and amavis. We changed debuglevel to 0 to prevent the log from filling up our entire hard disk.

Now we will modify SpamAssassin's main configuration file:

vi /etc/spamassassin/local.cf

And insert the lines:

bayes_path /var/lib/amavis/.spamassassin/bayes
auto_whitelist_path /var/lib/amavis/.spamassassin/auto-whitelist
whitelist_from spambin@example.com
lock_method flock
bayes_auto_learn_threshold_nonspam -0.5
razor_timeout 8

This insures both the root and amavis users use the same files and do not have to guess where they are, and whitelists our spambin. lock_method flock is used when the Bayes data resides on the local hard disk and is non NFS.

Optional: Since there is a script that runs each day to --force-expire old Bayes tokens "/etc/cron.daily/amavisd-new" (make sure there is if you use this setting!), we can set:

bayes_auto_expire 0

Optional: Some people believe auto-whitelist is more of a liability than an asset:

use_auto_whitelist 0

Possibly optional, possibly not: Depending on your setup, it might be necessary to explicitly set internal_networks and trusted_networks. The trust path tells spamassassin which clients are not trusted. See http://wiki.apache.org/spamassassin/TrustPath and this thread: # explicitly set our internal_networks (might be the same or similar to mynetworks) clear_internal_networks internal_networks 127/8 internal_networks internal_networks # add the same to trusted_networks, and possibly other computers/networks whose mail we trust clear_trusted_networks trusted_networks 127/8 trusted_networks trusted_networks

Save and exit the file. Please read http://spamassassin.apache.org/full/3.1.x/dist/doc/Mail_SpamAssassin_Conf.html at some point keeping in mind that some settings will have no effect when used with amavisd-new. Amavisd-new does not allow SpamAssassin to modify messages. You may also wish to set dns_available yes . With SpamAssassin version 3.1.x, additional configuration is needed:

vi /etc/spamassassin/v310.pre

To enable the ability to use DCC, uncomment the line:

#loadplugin Mail::SpamAssassin::Plugin::DCC

Since we are using SpamAssassin 3.1.1 or greater we can use the new sa-update feature. If you want to run sa-update without using GPG, run:

sa-update --nogpg

Optionally, you may first import the gpg key: cd /etc/spamassassin wget http://spamassassin.apache.org/released/GPG-SIGNING-KEY gpg --import GPG-SIGNING-KEY

Then simply run:


You should find the new rules in /var/lib/spamassassin/<SA version>. You should also run

amavisd-new -d config debug-sa

and verify SpamAssassin is locating all of its rule sets in /var/lib/spamassassin/<SA version>. You should also run:

su amavis -c 'spamassassin --lint'

after an update, and you should be aware you must reload amavisd-new after the update in order for the new rules to be used. It is important that sa-update completes without error. Optionally: crontab -e

and insert (on the first available blank line): 05 05 * * * /usr/bin/sa-update && /usr/bin/spamassassin --lint && /etc/init.d/amavis restart

During the time amavisd-new is restarting, mail cannot be delivered to it. Postfix will complain "connect to localhost[]: Connection refused". Postfix will defer this mail (for about 15 minutes). To speed things up, an impatient person may run 'postfix flush' to flush the deferred queue, but I would not.

chown -R amavis:amavis /var/lib/amavis
chmod -R 750 /var/lib/amavis
su amavis -c 'sa-learn --sync'

Since we've moved stuff into one of the amavis directories, we used 'chown' to refresh amavis's ownership of the entire tree. This is important. We need to do this any time we place files in the amavis directory that amavis does not already own. You should not have to run 'chmod' again. We also ran sa-learn to create the initial Bayes data.

If you would like to see if SpamAssassin and Razor are working, run spamassassin with the debug (-D) option (run this a couple times):

spamassassin -D </root/sample-spam.txt

Notice that DCC is not working. That's because we have not installed it yet.

If you debug spamassassin as user root I recommend you refresh file ownership every time:

chown -R amavis:amavis /var/lib/amavis

A note on Bayes: to better train the Bayes database we need to give it some examples of ham. The problem is, sa-learn --ham /path/to/hamfiles works on files that reside on the spamfilter. We don't keep mail on the spamfilter however. This problem can be solved by using your email client (MUA) to individually save messages in .EML format. Look for this option among the menu choices or 'Save As'. Edit a sample .EML file to insure the file looks like plain text. If it is full of garbage characters, then it cannot be used. Use WinSCP to copy your ham collection to an empty folder on your spamfilter. Then run sa-learn. Pick messages that have some substance to them so the database has something to work with. Use this especially when you receive a message that is tagged as spam, but is in fact ham. Autolearning (bayes_auto_learn) is turned on by default so the system will have no problem gathering plenty of spam. I suggest you only feed it additional examples of ham to begin with. In the future you will want to feed it samples of low scoring spam.

SpamAssassin has the ability to store its Bayes data in a MySQL database. If you are familiar with MySQL (or not) and you wish to improve performance, you should consider using it. Here is my HOWTO to get you going: http://www200.pair.com/mecham/spam/debian-spamassassin-sql.html


****************************************************** Installing DCC: Index ****************************************************** DCC is available from the Debian archives:

apt-get install dcc-client

Note that as of version 1.3.0 of DCC http://www.commtouch.com/ has exclusive marketing rights for DCC. If you resell anti-spam solutions that use DCC and you do not provide your DCC data to the public, you will need to pay for DCC. Please read the license.

The double ampersands let you run those 3 commands on one line. You will see 'done' if all goes well. Place a link to cron-dccd in our path: cd ln -s /var/dcc/libexec/cron-dccd /usr/bin/cron-dccd

Test our installation with:

cdcc info

We should get 'requests ok' from the servers. The instructions say to run cron-dccd each day to clean things up, so we will do that. crontab -e

and insert (on the next available blank line): 43 11 * * * /usr/bin/cron-dccd

Make sure you have a carriage return at the end of the line, then save the file (same command as vi) You are probably getting familiar enough to understand some of what's going on here. The cron-dccd clean-up program will run every day at 11:43am. We made the symbolic link to cron-dccd so it would be in our executable path, per DCC's instructions. For newbies who would like to understand cron: http://www.unixgeeks.org/security/newbie/unix/cron-1.html

Now test it with SpamAssassin:

su amavis -c 'spamassassin -D </root/sample-spam.txt'

You should see "dcc: got response" if all is well. If all is not well, it's probably the firewall issue we discussed above. If you just can't get Razor or DCC or Pyzor working properly, you should disable them in SpamAssassin's configuration file to prevent SpamAssassin from wasting its time trying to make them work. SpamAssassin will use all three by default. You have to tell SpamAssassin not to use them. If one of them is broken, you would edit /etc/spamassassin/local.cf and comment out the offending party as needed:

use_razor2 0
use_pyzor 0
use_dcc 0

I hope you got them all working because they really are valuable resources in the fight against spam. I have noticed over the last year that fewer and fewer people are submitting spam to the pyzor servers with the result being fewer and fewer messages are tagged by pyzor.

Now give it the full blown amavisd-new and SpamAssassin test:

amavisd-new stop
amavisd-new debug-sa

What can I tell you? It works fine on my computer. You should see nothing but happiness (except for the "No $unfreeze, not using it" type stuff).

Please stop amavisd-new at this time with [Ctrl]+c.

Normally SpamAssassin runs the 'dccproc' program for each message that it processes. If you have 30MB RAM to spare, you may benefit from running the daemonized version of the DCC client 'dccifd'. I personally recommend you have a system with at least 384MB RAM to do this. Note that if you were unable to get DCC working before, enabling dccifd will not solve the problem and should not be attempted. Optional to enable dccifd:

vi /etc/spamassassin/local.cf

and insert: dcc_home /var/dcc

save and exit, then: vi /var/dcc/dcc_conf

and change DCCIFD_ENABLE=off to: DCCIFD_ENABLE=on

Then change: DBCLEAN_LOGDAYS=14 to: DBCLEAN_LOGDAYS=1 save and exit.

If you choose to allow logging, cron-dccd should delete old log files when it runs. Keep your eye on the files that accumulate in the /var/dcc/log directory. It's your choice, but I personally don't want to monitor the DCC logs, so I turn off logging altogether by deleting the log directory and commenting out the logdir entry in dcc_conf: rm -r /var/dcc/log vi /var/dcc/dcc_conf and comment out: DCCIFD_LOGDIR="$DCCM_LOGDIR"

We will use a supplied script (rcDCC) to automatically start dccifd when we boot up: cp /var/dcc/libexec/rcDCC /etc/init.d/adcc update-rc.d adcc defaults

Update file ownership: chown -R amavis:amavis /var/dcc

Because we enabled dccifd in dcc_conf, we can start up dccifd by running the script: /etc/init.d/adcc start

If you deleted the log directory, you can expect an error message: "log thresholds set with -t but no -l directory". Now test that SpamAssassin finds dccifd: su amavis -c 'spamassassin -D </root/sample-spam.txt'

You should see dbg: dcc: dccifd got response:

local dns cache

****************************************************** Local DNS cache: Index ****************************************************** Having a local DNS cache is highly recommended provided you currently do not have a DNS server or other server that provides a DNS caching function on your network and you have sufficient available memory. I have found that using a broadband router (or similar) as a primary name server does not provide the same functionality a true DNS server provides. Name server settings are located in /etc/resolv.conf. If you choose not to use a local DNS cache then at least use a real DNS server as your primary. I have seen SpamAssassin time out on RBL lookups if it cannot perform DNS queries quickly enough. This can have a big effect on the final spam score. I will not pretend that I understand the intricacies of the bind9 program that we will install. We will configure bind9 to be a caching only name server with the option of forwarding requests to another server. You may also consider providing the service we install on this machine to other machines on your network. Note that you will need to modify our local firewall (iptables) if you choose to provide this service to other machines:

iptables -A FIREWALL -p udp -m udp --dport 53 -j ACCEPT
iptables -A FIREWALL -p tcp -m tcp --dport 53 -j ACCEPT

(or for enhanced security, only allow access from clients on our network):

iptables -A FIREWALL -p udp -m udp -s --dport 53 -j ACCEPT
iptables -A FIREWALL -p tcp -m tcp -s --dport 53 -j ACCEPT

See the "Create Firewall Rules:" section above.


Also note that your /etc/apt/sources.list will need to have "contrib" sources listed (as shown above in the "Change apt-get settings:" section). If you add "contrib" sources, make sure you run "apt-get update" afterwards.

Other good sources of information are http://www.lifewithdjbdns.org/ and http://www.fredshack.com/docs/djbdns.html and http://publibn.boulder.ibm.com/doc_link/en_US/a_doc_lib/files/aixfiles/resolv.conf.htm.

Read the notes above to determine if you need a local DNS cache before continuing. Back up our resolv.conf file:

cp /etc/resolv.conf /etc/resolv.conf-original

Download the daemontools installer:

apt-get install daemontools-installer

Per the instructions, install daemontools (just hit [Enter] at any questions it asks):


The svscan daemon will now be running. It runs programs it finds in the /service directory that daemontools created. Download the UCSPI-TCP installer:

apt-get install ucspi-tcp-src

Install UCSPI-TCP (just hit [Enter] at any questions it asks):


Download the djbdns installer:

apt-get install djbdns-installer

Install djbdns (just hit [Enter] at any questions it asks):


Configure the dnscache program:

dnscache-conf dnscache dnslog /etc/dnscache

Create a symlink to the dnscache program in the /service directory so svscan will start it:

ln -s /etc/dnscache /service

Wait at least 5 seconds, then see if the dnscache service is running:

svstat /service/dnscache

Create a new resolv.conf (pointing to ourselves as the DNS server):

echo "domain example.com" > /etc/resolv.conf
echo "nameserver" >> /etc/resolv.conf

Test that you are able to resolve a host name on the Internet:

dnsip www.cnn.com

We changed resolv.conf and passwd files, so we need to give Postfix new copies:


Tail the log file to verify dnscache is working: tail -40 /service/dnscache/log/main/current

If you can't get this to work, I would check your firewall settings. If you need to disable this, copy your original resolv.conf back (then run LINUX2 again). My systems worked fine for months and months. If you see a problem """unable to resolve host names""" that means that your rounter is unable to handle traffic. Other couse might be that resolf.conf has changed (maybe you run dhclient).


The bind9 manual is available at http://www.bind9.net/manual/bind/9.2.4/Bv9ARM.html and I wish to thank this document for much of the information listed here: http://www.falkotimme.com/howtos/perfect_setup_debian_sarge/index.php

Now we install bind9: We will install version 9.3.2 of bind9: apt-get install bind9

For security reasons we want to run BIND chrooted so we will perform the following steps: /etc/init.d/bind9 stop

Edit the file /etc/default/bind9 so that the daemon will run as the unprivileged user 'bind', chrooted to /var/lib/named: vi /etc/default/bind9

Modify the line: OPTIONS="-u bind" so that it reads: OPTIONS="-u bind -t /var/lib/named"

Create the necessary directories under /var/lib: mkdir -p /var/lib/named/etc mkdir /var/lib/named/dev mkdir -p /var/lib/named/var/cache/bind mkdir -p /var/lib/named/var/run/bind/run

Then move the config directory from /etc to /var/lib/named/etc: mv /etc/bind /var/lib/named/etc

Create a symlink to the new config directory from the old location (to avoid problems if bind is upgraded in the future): ln -s /var/lib/named/etc/bind /etc/bind

Make null and random devices, and fix permissions of the directories: mknod /var/lib/named/dev/null c 1 3 mknod /var/lib/named/dev/random c 1 8 chmod 666 /var/lib/named/dev/null /var/lib/named/dev/random chown -R bind:bind /var/lib/named/var/* chown -R bind:bind /var/lib/named/etc/bind

We can start up bind9 at this point: /etc/init.d/bind9 start

Let's see if the service is running: lsof -i | grep :domain

It is also imperative that after each change we make, we look in our syslog to see if bind9 reported any errors. Here we use less to view syslog. Once we are viewing the file, use an uppercase 'G' to go to the bottom of the file (and a lowercase 'q' to quit): less /var/log/syslog

We are setting up bind9 as a local caching only name server (later we will optionally configure it as a forwarding server). Here we add some additional security measures that prevent unauthorized machines from using our name server: vi /etc/bind/named.conf.options

On the line below "directory" we want to add a line that restricts use of our name server to the network our spamfilter is on. Place a [Tab] in front of the entry so it lines up with the other entries. You can add more than one network here if you like. Place a ";" (semicolon) after each network. Note that if you actually want to allow other clients to connect to our name server, as explained in the notes above you would also have to modify IP tables to allow this. allow-query {;};

Save and exit the file, then I would restart bind9 and check that it is running: /etc/init.d/bind9 restart lsof -i | grep :domain

Optionally configure bind9 as a forwarding server. Bind9 as we have it configured now will first query the root servers for hints when needed. I prefer to forward queries to another name server instead. There are advantages and disadvantages in doing this, but I prefer it. It is absolutely imperative that any name servers listed here are known to work from our spamfilter. These will almost certainly be the primary and secondary servers you currently have configured in /etc/resolv.conf (not, and not the IP address of the local machine) or your ISP's servers. Add the 'forwarders' entry just below the 'allow-query' entry we just made: vi /etc/bind/named.conf.options and add: forwarders {444.444.444.444; 555.555.555.555;}; To never query the root servers, optionally add (personally I do add this): forward only;

Save and exit the file, then once again I would restart bind9 and check that it is running: /etc/init.d/bind9 restart lsof -i | grep :domain

And once again, check for errors: less /var/log/syslog

Once it is determined bind9 is functioning, you can change the primary nameserver in /etc/resolv.conf: vi /etc/resolv.conf

and replace the entry for the primary nameserver (the first one listed): nameserver 444.444.444.444 to the IP address of this machine (our real IP address, not nameserver

Save and exit the file, then test that we are able to resolve host names: dig yahoo.com

You should see valid data, and the output will also tell you which name server was used to find the information: ;; SERVER:

Make sure this is shows our IP address as configured in /etc/resolv.conf. Now we can tell Postfix to use the new name server: LINUX2

Post Installation


Test the Installation:

Index ****************************************************** Let's start off fresh: reboot logout

If you happen to see the message "SpamAssassin Mail Filter Daemon: disabled, see /etc/default/spamassassin"; please ignore it, we do NOT want to enable spamd.

Other mail servers will need to find your server. Set up name resolution of sfa.example.com to its IP address. How this is done depends on your environment. Basically, you need to make sure that any box that needs to talk to this mail server can resolve its name, either through appropriate DNS server entries somewhere, or local "hosts" files on those machines.

Now let's see if this box is actually an email server! Add a new entry in the hosts file on your Windows computer that points to the spamfilter: sfa.example.com

You should already have a mailbox set up for "spambin". Create a user in your email client (MUA) for "spambin" so you can send and receive email from that account if you have not already done so. Temporarily set your email client's SMTP (Outgoing) server to sfa.example.com for the "spambin" account so any mail it sends gets sent back through the spamfilter. It is required however to whitelist "spambin" so the email doesn't end up back in the "spambin". This is the problem with forwarding email from the "spambin" (or "banned" or "virii") client. Any email you forward out of these mailboxes may end up back in the quarantine. Once we are done testing, you should set up the "spambin", "banned" and possibly "virii" email clients to send their email directly to the Exchange server. Of course you would never actually forward viruses to end users or open any viruses in this quarantine, but you may occasionally find legitimate mail that was quarantined due to a banned attachment. You should obviously have virus protection on the client machine.

Send yourself an email from the "spambin" account. Wait a minute, and then "Get new mail" or "Send and Receive" or whatever. If you don't get the email "spambin" sent you, obviously "Houston, we have a problem". You might check the mail log on the spamfilter for clues:

less /var/log/mail.log

If you would like to see the log go by in real time: tail -f /var/log/mail.log I use this command extensively, and I suggest you use it after any changes are made to Postfix or amavisd-new. This will tell you if your mail system is receiving and processing mail, or if your change just killed the system.

and/or use amavisd-new stop amavisd-new debug-sa for more detail.

You can increase the level of detail reported by adjusting $log_level in amavisd.conf. Remember to set it back to 0 when finished with your debug session.

cd /var/mail Then less any files you may find there. There may be a file or two that ended up there before Postfix was configured. Also try the commands mailq and qshape (and qshape deferred ) to see if there is mail stuck in the queue. Use amavisd-new debug while you are sending mail through the system to help provide clues to the problem. Open another terminal window and run mailq while the other window is running amavisd-new debug . If you made changes to configuration files and want to flush the queue, try postconf -f and if that does not work try postsuper -r ALL . See http://www.postfix.org/postsuper.1.html. Insure that the relay_domains parameter has been configured correctly. Inspect the /etc/postfix/transport file for errors, and make sure you run postmap /etc/postfix/transport every time you make changes.

If you have problems, the most likely reason is a typographical error, or a wrong IP or network address in one of the configuration files. Hopefully, you know Unix/Linux is cAse senSitiVe. Maybe you accidentally skipped one of the configuration steps. Some of the steps cannot be performed more than once however, so be careful. Remember, read /var/log/mail.log as a first step.

If you do get the email back, change whatever setting or use whatever command or tool you have that will enable you to look at the full headers of the email message. Examine the headers and behold your creation. If you sent an empty message with no subject, Pyzor might just flag it as spam!

As time goes by be sure to keep an eye on the number of files and temporary directories that are created in the /var/lib/amavis directory and its subdirectories. If there are a large number of files and/or temporary directories it would indicate some sort of problem. If you choose to keep quarantined messages on this box instead of sending them to spambin@example.com then they should accumulate in the virusmails directory; that would be considered normal. I have seen on many occasions people report that amavisd-new fails to delete temporary directories (their name begins with amavis-20) and there seems to be a lack of understanding as to the reason this occurs. It may possibly indicate a problem with one of the shared libraries that amavisd-new uses (uulib zlib etc.) or a problem with Perl itself. See http://www.ijs.si/software/amavisd/#faq-gen. I have seen reports of people writing scripts that delete these temporary directories on a regular basis to work around the problem but this is only sweeping the underlying problem under the rug.

Whenever you edit a few certain files like the hosts file on the spamfilter, we need to supply Postfix with an up to date copy of it or will complain: warning: /var/spool/postfix/etc/hosts and /etc/hosts differ LINUX2

postfix check

Congratulations, you did a great job. It's either time for that 4th cup of coffee, or maybe just finish the next few sections and call it a day, because in many respects, we are just getting started.



Installing ClamAV:

Index ****************************************************** This entire section is optional but recommended. It would be a good idea to get ClamAV configured and running, even if you choose to disable it. It's reasonably easy to turn it on and off. If you use this product regularly, consider a donation. It's also a good idea to read the mailing list archives http://lurker.clamav.net/list/clamav-users.en.html and join the clamav-announce mailing list http://lists.clamav.net/cgi-bin/mailman/listinfo/clamav-announce so you will be notified of new releases. Keep in mind that after a new version is released, it may take a couple days for the Debian package maintainer to update Debian.

Read http://www200.pair.com/mecham/spam/clamav-amavisd-new.html if you would like to gain a better understanding of what we are doing here.

apt-get update

Then install clamav, and clamav-daemon: apt-get install clamav clamav-daemon

Now, very important, add the clamav user to the amavis group: gpasswd -a clamav amavis

Now we configure amavisd.conf so amavisd-new will use ClamAV: vi /etc/amavis/amavisd.conf

To enable virus scanning, make sure this line is commented out (like this): # @bypass_virus_checks_maps = (1); # uncomment to DISABLE anti-virus code

Locate the line: @av_scanners = (

Uncomment these 4 lines, then make sure the value after CONTSCAN reads as follows:

While you are at it, if you would like to clean up amavisd.conf a little, you may optionally delete all the virus scanners between ClamAV and BitDefender. We want to keep BitDefender. It would be a very good idea to make a backup copy of amavisd.conf before you do this. Note that this /var/run/clamav/clamd.ctl value shown above must match the LocalSocket parameter in /etc/clamav/clamd.conf Change it here if necessary to match what is in /etc/clamav/clamd.conf.

The configuration file for ClamAV 0.88.6 is /etc/clamav/clamd.conf. The freshclam daemon (or cron job) is set to check for, and download if necessary, new virus definitions 12 times per day. The configuration file for freshclam is /etc/clamav/freshclam.conf You can check the log files at /var/log/clamav/freshclam.log and /var/log/clamav/clamav.log The startup script for freshclam is /etc/init.d/clamav-freshclam and for clamd it's /etc/init.d/clamav-daemon If you chose cron for database updates, the file is /etc/cron.d/clamav-freshclam. You can also research additional clamd.conf configuration options by running man clamd.conf

Let's reboot (it might make a difference), and then test the system: reboot logout

As an alternate to rebooting, you can stop and start clamd and amavisd-new: amavisd-new stop /etc/init.d/clamav-daemon stop /etc/init.d/clamav-daemon start amavisd-new start

Once the system comes back up, we need to test ClamAV. To do so, we can simply watch the mail.log go by as we send the Eicar test virus through the system: tail -f /var/log/mail.log

Send the Eicar test virus through as described below. After you are finished sending the virus through, use [Ctrl]+c to return to the shell prompt.

Once this machine is up and running in a production environment you should only reboot when necessary. There are many processes writing to the disk in this system and killing those processes is sometimes not a good idea.

Now you need to send a test virus to yourself, like eicar.com.txt from http://www.eicar.org/anti_virus_test_file.htm. Note: rename eicar.com.txt to something like eicar.txt because amavisd-new bans files with double extensions. Attach eicar.txt to the email you send. Don't use eicar.com or eicar_com.zip. Of course you would have to temporarily disable your desktop antivirus software first. You can use tail -f /var/log/mail.log so you can see what happens.

If ClamAV is not working you may get "Can't connect to UNIX socket". This could indicate a couple of things. The LocalSocket parameter in /etc/clamav/clamd.conf must be the same as the one in /etc/amavisd/amavisd.conf as noted above. The clamav user must also belong to the same group that the amavis user belongs to so both users can write to the UNIX socket file, in our case "clamd.ctl".

I have a funny story. I had this all working fine but it appeared that clamd thought that the eicar_com.zip file was "OK", in other words, it scanned it, but did not detect that is was a virus. It turned out my Internet proxy (WinProxy) had removed the virus from inside the file before I scanned it! It took me an hour to figure it all out.

If you have problems that you can't seem to solve, or you are upgrading to a new major release, completely uninstall the program, and then try another version if available:

apt-get --purge remove clamav clamav-base clamav-daemon clamav-freshclam libclamav1

Watch for errors as the program is being uninstalled, you may have to manually remove any clamav directories that dpkg failed to remove (rm -r). Be extremely careful here!.

If you just can't get it working, uncomment @bypass_virus_checks_maps in /etc/amavis/amavisd.conf to disable virus scanning (or go shopping for another antivirus vendor). Also: make sure everything works AFTER you reboot. Don't leave ClamAV in a non-functional state if you have virus scanning enabled. Amavisd-new will not work properly. Keep an eye on /var/log/clamav/freshclam.log and /var/log/clamav/clamav.log. You need to look for error messages in these files. You may have an error or two when the program is first installed; this is probably OK and may be due to things happening out of sequence. Check the logs for a couple days and make sure the database updates do not fail and that Clamd is notified of updates.

When it is time to upgrade to a new version of ClamAV: Run 'apt-get update'. If you are upgrading to a MAJOR new version, completely uninstall ClamAV as described above. Install the new version of clamav and clamav-daemon. Run 'gpasswd -a clamav amavis'. I suggest rebooting, if possible. Run 'tail -f /var/log/mail.log', and send a test message containing the eicar "virus" through.

There is a third party http://www.sanesecurity.com/clamav/ that maintains additional anti-phishing and scam mail signatures. If you would like to add these I have customized for Debian one of the scripts used to download the signatures: Optionally use additional anti-phishing and scam signatures: cd /usr/sbin wget http://www200.pair.com/mecham/spam/scamp.sh chmod +x scamp.sh

Always remember that stuff you download can be forged. I suggest you glance through the script: less scamp.sh

Then run the script (if it looks like it's not a script that destroys the planet): scamp.sh

It should have produced something like: Updated: phish.ndb Thu Nov 23 08:48:38 MST 2006 Updated: scam.ndb Thu Nov 23 08:48:39 MST 2006

and if you look at the list of clamav signatures, you should see these have been added: ls -l /var/lib/clamav

Per the instructions, add an entry to your crontab: crontab -e

Set MM to three minutes from now: MM */4 * * * /usr/sbin/scamp.sh

At some point in the future you may get tired of wading through all the comments in amavisd.conf. Here's how to remove them: Optionally remove most comments from amavisd.conf: cp /etc/amavis/amavisd.conf /etc/amavis/amavisd.conf-verbose grep -vE '$|#' /etc/amavis/amavisd.conf > /etc/amavis/amavisd.conf-temp cp /etc/amavis/amavisd.conf-temp /etc/amavis/amavisd.conf


Tweaking Notification Settings:

Index ****************************************************** This may be a good time to experiment with some of the notification settings in amavisd.conf. Change some of these settings and send yourself email containing viruses, banned attachments, spam, and attachments with double extensions. Do one thing at a time and take notes on what happens and who gets notified. Remember to stop and start (or debug) amavisd-new after each change. Settings to play with are: $final_virus_destiny $final_banned_destiny $final_spam_destiny $final_bad_header_destiny $warnvirussender $warnspamsender #(not really used any more) $warnbannedsender $warnbadhsender $warnvirusrecip $warnbannedrecip $warn_offsite

You can uncomment and set $spam_admin if you would like to get detailed diagnostic messages for each spam: $spam_admin = "postmaster\@$mydomain";

Play with these until you have everything the way you prefer it (as far as notification and destination of all the garbage email goes). Experiment with them a little to get an idea of how they work. I recommend D_DISCARD for $final_virus_destiny in this day and age. Since many modern viruses and worms (like MYDOOM) fake the sender, D_BOUNCE just creates extra useless and confusing Internet traffic and it also clogs up your queues with mail that can't be delivered. It will still quarantine the message and notify the postmaster when a virus is found. If you would like all email containing a virus (or a banned attachment) to disappear into a black hole, set $virus_quarantine_to = undef;.


Back up critical files:

Index ****************************************************** Let's back up some of our hard work to a floppy. Grab a plain old High-Density 1.44MB floppy disk, and head on over to the spamfilter. Insert the floppy, and then head back to your Windows machine. Or just type this stuff in at the console if it's a long walk: We may have to create a device if it does not exist:

test -e /dev/fd0u1722 || mknod /dev/fd0u1722 b 2 60 chmod 660 /dev/fd0u1722 chown root:floppy /dev/fd0u1722

Create the mount point:

mkdir /floppy

Format the floppy (insert it first of course):

fdformat /dev/fd0u1722

Create a file system on the floppy (we need one that accepts long file names):

mke2fs /dev/fd0u1722

Mount the floppy:

mount /dev/fd0u1722 /floppy

Yes I know, working with floppies in *nix is a pain. And copy all these files to it: (Yes you can copy and paste this whole section).

cp /etc/fstab /floppy cp /etc/aliases /floppy cp /etc/postfix/main.cf /floppy cp /etc/postfix/master.cf /floppy cp /etc/postfix/sender_access /floppy cp /etc/postfix/transport /floppy cp /etc/postfix/virtual /floppy cp /etc/postfix/relay_recipients /floppy cp /etc/postfix/body_checks /floppy cp /etc/postfix/header_checks /floppy cp /etc/amavis/amavisd.conf /floppy cp /etc/spamassassin/local.cf /floppy cp /var/lib/amavis/.spamassassin/user_prefs /floppy cp /var/lib/amavis/.razor/razor-agent.conf /floppy cp /etc/apt/sources.list /floppy cp /etc/apt/preferences /floppy cp /etc/clamav/clamd.conf /floppy cp /etc/clamav/freshclam.conf /floppy

Wait a minute for the files to copy over, and then list the floppy disk's contents: ls -l /floppy

This floppy will not be readable by a Windows machine. I can't repeat this enough: Always unmount the floppy before you remove it: I suggest you have the monitor on at the console so you can see the mess you make if you don't.

umount /floppy

Remove it, label it and store it in a safe place.

If you wanted to restore the files at some point in the future:

mount /dev/fd0u1722 /floppy

cp /floppy/aliases /etc/aliases newaliases

cp /floppy/main.cf /etc/postfix/main.cf cp /floppy/master.cf /etc/postfix/master.cf cp /floppy/sender_access /etc/postfix/sender_access postmap /etc/postfix/sender_access

cp /floppy/transport /etc/postfix/transport postmap /etc/postfix/transport

cp /floppy/virtual /etc/postfix/virtual postmap /etc/postfix/virtual

cp /floppy/relay_recipients /etc/postfix/relay_recipients postmap /etc/postfix/relay_recipients

cp /floppy/body_checks /etc/postfix/body_checks cp /floppy/header_checks /etc/postfix/header_checks cp /floppy/amavisd.conf /etc/amavis/amavisd.conf cp /floppy/user_prefs /var/lib/amavis/.spamassassin/user_prefs cp /floppy/local.cf /etc/spamassassin/local.cf cp /floppy/razor-agent.conf /var/lib/amavis/.razor/razor-agent.conf cp /floppy/clamd.conf /etc/clamav/clamd.conf cp /floppy/freshclam.conf /etc/clamav/freshclam.conf cp /floppy/sources.list /etc/apt/sources.list cp /floppy/preferences /etc/apt/preferences apt-get update

umount /floppy

then shutdown and restart amavisd-new and Postfix as needed. Note that we do not restore /etc/fstab, it is just a real good idea to have a copy of to refer to. It describes our partition layout.

If you have an ftp server that you can upload files to, (maybe you got 10MB of web space with a dial up account you have) I will quickly describe backing up the files to that server. It's a good idea to have 2 terminal windows open so we can have ftp running in one, and the command line in the other. Stop Postfix and amavisd-new so the bayes files are not written to during the backup: postfix stop amavisd-new stop su amavis -c 'sa-learn --sync'

Start your ftp session (substituting your settings): ftp -p server.domain.tld

Enter your user name and password as requested, and then make a directory to place our files: ftp> mkdir sfa (only necessary the first time you do this)

Change to that directory: ftp> cd sfa

Then simply copy and paste this entire section:

ascii put /etc/aliases aliases put /etc/postfix/main.cf main.cf put /etc/postfix/master.cf master.cf put /etc/postfix/sender_access sender_access put /etc/postfix/transport transport put /etc/postfix/virtual virtual put /etc/postfix/relay_recipients relay_recipients put /etc/postfix/body_checks body_checks put /etc/postfix/header_checks header_checks put /etc/amavis/amavisd.conf amavisd.conf put /etc/spamassassin/local.cf local.cf put /etc/apt/sources.list sources.list put /etc/apt/preferences preferences put /etc/clamav/clamd.conf clamd.conf put /etc/clamav/freshclam.conf freshclam.conf put /var/lib/amavis/.razor/razor-agent.conf razor-agent.conf put /var/lib/amavis/.spamassassin/user_prefs user_prefs binary put /var/lib/amavis/.spamassassin/auto-whitelist auto-whitelist put /var/lib/amavis/.spamassassin/bayes_toks bayes_toks put /var/lib/amavis/.spamassassin/bayes_seen bayes_seen ls -l pwd quit amavisd-new start postfix start

Use get instead of put to restore a file. For example: get clamd.conf /etc/clamav/clamd.conf Don't get your servers mixed up if you have more than one!


Set up security reports:

Index ****************************************************** We are first going to install logcheck

apt-get install logcheck logcheck-database

Read the message that comes up. If you would like to change any settings:

vi /etc/logcheck/logcheck.conf

Take a moment to test logcheck. Open a second PuTTY session and log in as root but use the wrong password on your first attempt to log in. Now run su -s /bin/bash -c "/usr/sbin/logcheck" logcheck at the command prompt, wait a minute, and then check the mailbox of the address you configured logcheck to send email. You should get a message indicating the security violation. Logcheck looks for suspicious activity and is scheduled to run once each hour. You will only get a message if it finds something suspicious, but this is configurable. Don't set it to "paranoid", there would be an entry for every email that passed through the system. Read more about logcheck by using less /usr/share/doc/logcheck/README.logcheck If you get annoying repetitive emails from logcheck, try editing /etc/logcheck/ignore.d.server/logcheck and insert a regular expression of the text you wish logcheck to ignore. For example, I inserted CRON.*: \(pam_unix\) session opened for user CRON.*: \(pam_unix\) session closed for user

You most likely will not want to be annoyed by every message amavisd-new produces so install this file: cd /etc/logcheck/ignore.d.server wget http://www200.pair.com/mecham/spam/logcheck/amavisd-new

Logcheck will also look for keywords (like "attack") contained in the /etc/logcheck/cracking.d/logcheck file. We can tell logcheck to ignore log entries that contain a hostname such as "attackingthedevil.co.uk" by creating a new file in the appropriate logcheck "ignore" directory and placing that text in it. We create a file because none exist at this point: echo "attackingthedevil.co.uk" >> /etc/logcheck/cracking.ignore.d/logcheck-postfix

If you removed the DCC log directory as I suggested, dccifd will log an error every time it is called. We want logcheck to ignore those log entries (this is a single command): echo "stat\(log directory /var/dcc/log\): No such file or directory" >> /etc/logcheck/ignore.d.server/dcc

While we are at it, there is another dcc message we don't care about: echo ": missing message body" >> /etc/logcheck/ignore.d.server/dcc

and also: echo "detected 0 spam, ignored for 0, rejected for 0," >> /etc/logcheck/ignore.d.server/dcc

and a Postfix message I wish to suppress: echo "dsn=2.7.0, status=sent \(254 2.7.0 Ok," >>/etc/logcheck/ignore.d.server/postfix

For more information about logcheck rules and patterns to include or ignore: vi -R /usr/share/doc/logcheck-database/README.logcheck-database.gz and to debug logcheck: su -s /bin/bash -c "/usr/sbin/logcheck -otd" logcheck

Subscribe to http://lists.debian.org/debian-security-announce/ and visit http://www.debian.org/security/ You will get an email from them every time any one of approximately 15,000 programs in the Debian catalog have been found to have a security flaw, along with some instructions. You will not have many of those programs installed on your system. The 'stable' version of a security related software update is released first. The 'testing' and/or 'unstable' versions may take a couple weeks to get released. To do a quick check whether you have a program on your system, try: which [program name] or whatis [program name] or dpkg -l [package name]

And to get a somewhat full list of packages that are installed on your system: cd

Use dpkg and grep to send the list of installed program files to a file called "progs": dpkg -l '*' | grep '^i' > /root/progs

Then use less to view the file: less /root/progs

Or send it in an email to root: cat /root/progs | mail -s "sfa installed programs" root

Note that this will not include programs like DCC that you installed by means other than dpkg or apt-get.

I like to be notified each morning that the mail queue on our system is empty (or nearly empty, depending on how busy our system is) because if it is not, we may have a problem. Note that if you do not use the "relayhost" parameter in /etc/postfix/main.cf, you should have items in the mailq most of the time. These will most likely be NDRs that cannot be delivered. If the queue is full of legitimate email, the most likely cause is our Exchange server is down. If you don't get a mailq email at all, it is likely the spamfilter is down. We will only display the last 10 lines of output from the mailq command. crontab -e

And insert at the first available blank line (actually, this report is optional): 30 7 * * * /usr/bin/mailq |/usr/bin/tail |/usr/bin/mail -s "mailq sfa" root

While we are editing crontab, let's also sync our CMOS clock once each day, and for the forgetful type (forgot that you are not supposed to run 'sa-learn' as root) we will make sure 'amavis' still owns the Bayes and AWL files: 10 10 * * * /sbin/hwclock --systohc 30 17 * * * /bin/chown -R amavis:amavis /var/lib/amavis/.spamassassin

Save and exit

In addition to mailq (or as an alternate) you may wish to use qshape vi /etc/cron.d/qshape-cron

And insert (2 lines): PATH=/usr/sbin 31 7 * * * postfix /usr/sbin/qshape incoming active deferred 2>&1 |/usr/bin/mail -s "qshape sfa" root

Save and exit. Logcheck will now complain each day, so we need to shut it up: vi /etc/logcheck/ignore.d.server/postfix

and insert at the top of the file (1 line): ^\w{3} [ :0-9]{11} [._alnum-]+ postfix/pickup\0-9]+\]: [[[alnum]+: uid=[0-4]+ from=<postfix>


Set up intrusion detection:

Index ****************************************************** Don't start this section unless you have a good hour to work on it. This part drove me nuts for a couple of days. I have used tripwire on my Red Hat boxes and felt it was pretty straightforward after I understood the concepts and the commands. When I tried it on Debian (it is available with apt-get) it simply refused to run (segmentation faults and such). I could not find the cause after Googling for a good hour. Any way, I gave up and looked for alternatives. I decided to give AIDE a try since it was also available as a Debian package. Be forewarned you may not enjoy this part. Be aware that your Linux box is an ideal platform to launch an attack on your entire network. So implementing this is highly recommended.

The concept with AIDE is to take a snapshot of some of the characteristics of critical files on our system, and then store that information on read-only media; a write protected floppy for example. Then run a program that compares the current state of those files on our system with the database, and report any differences. We should be able to tell if a hacker has compromised our system if the characteristics of the files on our system differ from the files in the database.

There are some challenges with doing this. Obviously, during normal use, some files change, like log files. So one challenge is to cut down on the unnecessary "chatter" that appears in the report. Adding and removing programs is considered normal use but this type of activity will generate alarms. When we are at the point the report has grown and is causing us to spend more time reading it than it should, we generate a new database and move it to the read only media. We have to be sure our system has not been compromised at the time we create a new database, so it would be wise to run a report before any new "trusted" software is installed, then another one after, then create a new database so we don't have to look at all that activity on every subsequent report.

When we install the program, it sets everything up on the hard drive, allows us to create the database right off the bat and it sets up a cron job to send us a report each day. This is fine, but completely insecure. A Hacker could replace the program, so we have to move it to the write protected media. We are going to use a write protected floppy disk, for convenience. The configuration file could be hacked, so we have to move it. And the same thing goes for the script that generates the report. These all have to be moved to write protected media. We can add an entry in crontab to run the report script off the floppy, and we will, but keep in mind that this can be hacked also, so the only way to be sure the report has not been tampered with is to run it from the command line off the write protected floppy.

Let's install aide: For consistency, we are not using the most current version of AIDE:

cd /usr/local/src wget http://www.xmission.com/~jmcrc/aide_0.10-4_i386.deb dpkg -i aide_0.10-4_i386.deb

The installation will have three input screens, answer them as follows:

Daily reports are mailed to root by default. [Ok]

Initialize aide database? [No]

Before AIDE can be used, you will have to initialize a database. [Ok]

The installation should create these files: /usr/bin/aide = the executable program file /etc/aide/aide.conf = the configuration file /etc/cron.daily/aide = a nice script that runs the report

Of course, other files and directories were created, but these are the only files we care about at this time.

We are going to move these files to /root/aide then uninstall the program. Make a new directory, a convenient place to store the files we want: mkdir /root/aide

Then copy the files, note that we will rename the report script "report": cp /usr/bin/aide /root/aide cp /etc/aide/aide.conf /root/aide cp /etc/cron.daily/aide /root/aide/report

Then we uninstall aide: apt-get --purge remove aide

We will need recreate the directory that AIDE uses for its logs: mkdir /var/log/aide

Let's work on the configuration file: You can use the WinSCP editor if you prefer: vi /root/aide/aide.conf

Change: database=file:/var/lib/aide/aide.db To: database=file:/floppy/aide.db

Change: database_out=file:/var/lib/aide/aide.db.new To: database_out=file:/root/aide/aide.db.new

Under Custom Rules, edit Binlib, and remove: +m +c

Edit Devices, and remove: +i +g +c

under # Kernel, change: =/boot$ Binlib to: /boot Binlib

Comment out the entire section under # Log Files

Under # Check crontabs add: /etc/cron.d Databases /etc/cron.daily Databases /etc/cron.hourly Databases /etc/cron.monthly Databases /etc/cron.weekly Databases /etc/crontab Databases

Save and exit. These are only suggestions; you can tweak this to your hearts content. More info can be found at: http://www.cs.tut.fi/~rammer/aide/manual.html

Let's edit the report script: vi /root/aide/report

Change: PATH="/bin:/usr/bin" To: PATH="/floppy:/bin"

Change: CONFFILE="/etc/aide/aide.conf" To: CONFFILE="/floppy/aide.conf"

Change: [ -f /usr/bin/aide ] || exit 0 To: [ -f /floppy/aide ] || exit 0

If you would like to send the report to someone other than root, optionally change: MAILTO="${MAILTO:-root}" To something like: MAILTO="${MAILTO:-someuser@example.com}"

Change: DATABASE="${DATABASE:-/var/lib/aide/aide.db}" To: DATABASE="${DATABASE:-/floppy/aide.db}"

Change: COMMAND="${COMMAND:-check}" To: COMMAND="${COMMAND:-update}"

Change: aide $AIDEARGS --$COMMAND >"$LOGDIR/$LOGFILE" 2>"$ERRORTMP" To: aide $AIDEARGS --config=/floppy/aide.conf --$COMMAND >"$LOGDIR/$LOGFILE" 2>"$ERRORTMP"

Save and exit.

If you have a floppy in the drive, unmount it (umount /floppy) then remove it. Insert a floppy in the drive. We are going to format it, create an ext2 file system on it, mount it, and then copy the AIDE files to it. We may have to create a device if it does not exist:

test -e /dev/fd0u1722 || mknod /dev/fd0u1722 b 2 60 chmod 660 /dev/fd0u1722 chown root:floppy /dev/fd0u1722

Make sure we have a mount point: mkdir /floppy

Run these one at a time and wait for each command to finish: fdformat /dev/fd0u1722

mke2fs /dev/fd0u1722

fsck /dev/fd0u1722

mount /dev/fd0u1722 /floppy

Then copy these files over to the floppy: cp /root/aide/aide /floppy cp /root/aide/aide.conf /floppy cp /root/aide/report /floppy cp /usr/bin/head /floppy cp /usr/bin/cut /floppy cp /usr/bin/savelog /floppy cp /usr/bin/touch /floppy cp /usr/bin/wc /floppy cp /usr/bin/mawk /floppy/awk

Wait for the files to copy over (30 seconds). Now we can run the routine that creates the first database. We only need to run this once: /floppy/aide --config=/floppy/aide.conf --init

This creates aide.db.new in the /root/aide directory, this is the initial database and must be copied to the floppy as aide.db. cp /root/aide/aide.db.new /floppy/aide.db

Wait long enough (20 seconds) for the file to copy over, and then run the report: /floppy/report

Check your inbox for the report. You may want (or need) to fix a couple things in /floppy/aide.conf or /floppy/report. Then run the report again. Then copy /root/aide/aide.db.new to /floppy/aide.db again. The settings in aide.conf may need to be tweaked over the next couple weeks. You can check for errors by using cat /var/log/aide/error.log

Now you have to write protect the floppy disk. This is the most important part. umount /floppy

Then pull out the disk and push up the write protect tab. Reinsert the floppy, and mount it again: mount /dev/fd0u1722 /floppy

This floppy should remain in the drive all the time. (Unless we need to use the drive for a moment)

Each time you run the report, it reads the database /floppy/aide.db but it also creates a new aide.db.new database. So why do we care about the aide.db.new? It's a matter of convenience. If the report is getting kind of long, and there appears to be nothing in it you would not expect; the aide.db.new database reflects the current state of the system and could be used to replace aide.db. You replace your aide.db on the floppy with aide.db.new, just as you did when you first initialized the system. If you run the report again, it should be clean, unless files have changed since it was created. You need to understand the risks of relying on the quality of the aide.db.new database if you use the copy that was created during the cron job. The cron job could have been hacked. A hacker could manipulate the file. Only rely on the aide.db.new database if you run /floppy/report from the command line and you inspect the report just prior to copying it over to the floppy. If you left the write protection off the floppy drive for any length of time, it's possible you can no longer rely on the database. Be paranoid.

So here's the gist of maintenance:

Note that every time you make a change to the configuration file (aide.conf) you will need to run the report, and then copy the new database to the floppy, otherwise every file in the aide database may possibly be listed as "File /filename in databases has different attributes". This is not an indication the files have changed; it is an indication there is a mismatch between aide.conf and aide.db.

You could put the command /floppy/report in your crontab (we will do so), and have it run each day just before you normally open your email, but a hacker could send forged reports for weeks before you knew there was a problem. Be aware of the danger. For a trustworthy report simply run the report from a command line every day, few days, week, few weeks, month, whatever your level of paranoia permits.

crontab -e

And insert: 25 7 * * * /floppy/report

Save and exit

Ok, you should make a backup copy of the floppy, because floppies are not reliable: Change to our home directory: cd

Unmount the floppy, but leave it in the drive: umount /floppy

Create an image of the floppy and store it to a file: dd if=/dev/fd0u1722 of=floppy.img

dd stands for Copy and Convert' and was renamed to dd only because cc' was reserved for the C compiler. if= input file, of= output file

Remove the source disk, insert the destination disk: First, format the new floppy: fdformat /dev/fd0u1722

Then copy the image to the new floppy: dd if=floppy.img of=/dev/fd0u1722

Simply use the new disk now. Turn write protect on, then mount the floppy: mount /dev/fd0u1722 /floppy If you think about it for a minute, you will realize that one of these floppies can be used in another machine. You would create the /var/log/aide and /root/aide directories, copy /floppy/aide.db to /root/aide/aide.db.new, create the cron job and the startup script (our next item). Then run the report and copy aide.db.new over to /floppy/aide.db.

We will create a special startup script called /etc/init.d/startflop that runs when the system boots up. We will use this script to mount the floppy automatically when we boot up. There are other ways to accomplish this task, but this one works best. Depending on your hardware, you may need to set your BIOS to boot from the hard drive first to avoid it from attempting to boot from the floppy. vi /etc/init.d/startflop

And insert the following text just as it is listed here:

#! /bin/sh # # very simple startup script

case "$1" in


exit 0

Save and exit the file, then make the file executable: chmod +x /etc/init.d/startflop

Now use this command to enable it and prioritize it: update-rc.d startflop defaults 80

Now make a symbolic link to it, I will explain why in a moment: ln -s /etc/init.d/startflop /usr/bin/floppy

The symbolic link will make our life easier. Now, to mount the floppy simply run: floppy start and to unmount the floppy simply run: floppy stop Note that this can only be used to mount floppies that we formatted with "fdformat /dev/fd0u1722"

See how little free space we have on the floppy disk: df /floppy

Note that if you ever run out of room on the floppy, you can delete any of the files off the floppy that we copied over from the /bin directory (tempfile, hostname, cat, date, rm, grep) due to the fact that we included /bin in our path statement in /floppy/report. Only delete what is absolutely necessary.

See http://www.oreilly.com/catalog/debian/chapter/book/ch04_04.html for help with mounting devices.

****************************************************** CPAN, Pflogsumm and trim_whitelist: Index ****************************************************** We are going to install a couple utilities that will be of value to us. One is pflogsumm.pl that produces statistical reports. We will also install a script to maintain the auto-whitelist file. You could install pflogsumm via apt-get but doing it this way familiarizes us with CPAN.

We need to install a couple of programs using CPAN; CPAN is a system created to make it easier to install Perl modules. See http://www.cpan.org/ for more information about CPAN.

The first time you start up CPAN, it will ask you to configure it. We want to answer "yes" to configure it. We will accept all the default prompts except we need to use http mirrors and not ftp mirrors. If you have a proxy server in front of your spamfilter that requires user names or passwords or special settings, I can't help you with that. You'll just have to look elsewhere for answers. One more note: if you want to start the configuration process over again, at the cpan> prompt, enter o conf init

We need to set our system to use passive mode for ftp transfers: vi /etc/libnet.cfg

and add this to the list of settings: 'ftp_ext_passive' => 1,

Start a CPAN session: perl -MCPAN -e shell

Accept the default of "yes" at the: Are you ready for manual configuration? [yes] Accept all the defaults, eventually you will need to (and this may take some time to come up): Select your continent Select your country

After you have selected these, hit [space][enter] a few times until you see some http servers. Do not pick any ftp servers. Select a couple of the http servers. Hit [enter] to get back to the cpan> prompt. One more note: do not update the CPAN program itself.

Now let's install a couple of modules we need: At the cpan> prompt type these commands in exactly: install File::MMagic

If you are asked any questions, accept the defaults.

Back at the cpan> prompt: install Date::Calc

If you are asked any questions, accept the defaults. When it finishes, exit cpan with:


This section will set up an automated preparation of a very nicely laid out report of email activity, and email this report to us once per day, with the previous day's mail statistics. We need the pflogsumm.pl utility: Go to: http://jimsun.linxnet.com/postfix_contrib.html And by looking at the link to the program, edit these next lines if necessary to reflect the latest production version: cd /usr/local/src wget http://jimsun.linxnet.com/downloads/pflogsumm-1.1.0.tar.gz tar xzvf pflogsumm-1.1.0.tar.gz cd pflogsumm-1.1.0 cp pflogsumm.pl /usr/sbin chmod +x /usr/sbin/pflogsumm.pl cd /usr/sbin wget http://www200.pair.com/mecham/spam/pflogsumm-conn-delays-dsn-patch patch pflogsumm.pl <pflogsumm-conn-delays-dsn-patch rm pflogsumm-conn-delays-dsn-patch cd

Let's set up a cron.daily script that prepares and mails us the pflogsumm report. When I first wrote this HOWTO, the mail.log file rotated once each week. Now it seems to rotate sometimes once a day, sometimes twice a day and sometimes every couple days. I used to be able to create a weekly report when the mail.log files were rotated on a predictable basis but now I have to combine several log files just to be insured I have the data I need to report on the previous day's activity. cd /etc/cron.daily wget http://www200.pair.com/mecham/spam/pflogsumm chmod +x pflogsumm

You may need to edit the script and change the hostname just after the word "DAILY" to reflect your system's hostname. You may also want to change to whom the report gets mailed: vi /etc/cron.daily/pflogsumm

Notice that in order to insure we have all the previous day's data, we include the contents of all the files (mail.log*).

There is one major problem with the report. Any email that gets sent to amavisd-new, which includes most mail that isn't rejected at the front door, also comes back from amavisd-new. This means Postfix sees the email twice. So the report lists them twice. Sorry.

I suggest you read the pflogsumm.pl faq; your version number of pflogsumm may be different: less /usr/local/src/pflogsumm-1.1.0/pflogsumm-faq.txt Also see this manpage for pflogsumm: http://manpage.willempen.org/1/pflogsumm

FYI: /etc/crontab controls when the scripts in /etc/cron.daily /etc/cron.weekly and /etc/cron.monthly run. One of the scripts in /etc/cron.weekly is sysklogd. sysklogd reads its configuration from /etc/syslog.conf. You can see what logs should get rotated weekly by sysklogd by using the command syslogd-listfiles --weekly

You will notice that if you use SpamAssassin's auto-whitelist feature, over time the /var/lib/amavis/.spamassassin/auto-whitelist file will grow to a rather large size. The SpamAssassin source code comes with a utility called check_whitelist that can be used to trim the size down. Run perldoc check_whitelist to see how it is used. There is a modified version of check_whitelist called trim_whitelist we are going to use to reduce the size of the auto-whitelist file. This utility is explained here: http://article.gmane.org/gmane.mail.spam.spamassassin.general/59651. Download trim_whitelist: cd /usr/sbin wget http://www.deepnet.cx/~kdeugau/spamtools/trim_whitelist

Make it executable: chmod +x /usr/sbin/trim_whitelist

List our SpamAssassin directory: ls -l /var/lib/amavis/.spamassassin

Run the program in order to test it: su amavis -c '/usr/sbin/trim_whitelist'

List our SpamAssassin directory again: ls -l /var/lib/amavis/.spamassassin

If the test is successful, the program will have created a new file: auto-whitelist-old

Now we will create a cron job so trim_whitelist will run once each week: cd /etc/cron.weekly wget http://www200.pair.com/mecham/debian/trim_whitelist_weekly chmod +x trim_whitelist_weekly cd

****************************************************** Whitelisting, Blacklisting, Tweaking: Index ****************************************************** Postfix, Amavis and SpamAssassin all have methods to do whitelisting and blacklisting. Postfix has a number of methods to reject mail before it enters the system, we configured some and I provided links to others during the Postfix Anti Spam configuration. We also discussed /etc/postfix/sender_access that can be used to blacklist senders. We created /etc/postfix/header_checks and /etc/postfix/body_checks that can be used for content filtering and I provided links to some examples. The files themselves also provide examples. When we were editing /etc/amavis/amavisd.conf you noticed sections that dealt with whitelisting and blacklisting. It is recommended you do "soft" whitelisting and blacklisting by adding entries to the @score_sender_maps section of amavisd.conf. Add your entries in the same section that 'nobody@cert.org' => -3.0, is listed. Negative scores will be subtracted from the overall spam score, and positive scores will be added.

Note that Postfix and Amavis will need to be shutdown and restarted (or reloaded) after making changes to configuration files: postfix reload will cause Postfix to reload its configuration files /etc/init.d/postfix restart will shutdown and restart Postfix, and so will: postfix stop postfix start

/etc/init.d/amavis stop /etc/init.d/amavis start is the best way to handle Amavis, but this works as well: amavisd-new stop amavisd-new start as does this: amavisd-new reload

You can stop and restart amavisd-new while Postfix is running. Delivery to amavisd-new will fail (and you will get errors in the log), but Postfix will queue the mail in the deferred queue. If amavisd-new has only been down for a moment, Postfix will try to send the mail again in about 16.6 minutes (1000 seconds). If you are impatient, or amavisd-new has been down for a longer period, you may wish to use 'postfix flush' to force Postfix to attempt delivery of the mail currently in the deferred queue. If you have made changes to the way postfix communicates with amavisd-new (for example you comment out content_filter in main.cf to bypass amavisd-new) you may need to requeue the mail with postsuper -r ALL

Configuring and tweaking SpamAssassin is an art in itself. There is plenty of information on the Internet to help guide you through this. I will simply supply a few tweaking links for you to explore. Don't forget that it is possible to write custom rules with negative numbers that can be used to lower the score. Keep in mind that many custom rules once only available as add-ons are now integrated into SpamAssassin version 3, so do some research to find out if you are duplicating rules.

Many people use by Rules Du Jour, but remember, if you use a lot of custom rules, you can use more than 100MB RAM for each amavisd process (and create a major load on the system). Because some of these rule sets are updated frequently it increases the possibility that a rule set may have an error in it. If this happens it could halt your server. NEVER use blacklist.cf, blacklist-uri.cf or bigevil.cf. I suggest you go slow, add one at a time, then wait a day or so and check your memory usage: http://www.exit0.us/index.php?pagename=RulesDuJour

As far as custom rules go, I personally use http://www.rulesemporium.com/rules/mangled.cf

I also download a set of the safest SARE rules: http://marc.theaimsgroup.com/?l=spamassassin-users&m=115637139728022 cd /etc/spamassassin wget http://saupdates.openprotect.com/pub.gpg sa-update --import pub.gpg sa-update --gpgkey D1C035168C1EBC08464946DA258CDB3ABDE9DC10 --channel saupdates.openprotect.com spamassassin --lint

and if everything looks OK: /etc/init.d/amavis restart Personally I use sa-update, and the OpenProtect SARE rules shown in the link above. Once these are properly configured, you could use something like my script that downloads updates from both places, and if updates are downloaded from one or he other, amavisd-new is restarted: cd /usr/sbin wget http://www200.pair.com/mecham/spam/sa-update.sh chmod +x sa-update.sh You would place /usr/sbin/sa-update.sh in your crontab (replacing the existing sa-update command).

And here is a note on how to use sa-update instead of RulesDuJour: http://marc.theaimsgroup.com/?l=spamassassin-users&m=115545719618240

Remember, adding custom rule sets will require additional RAM. Use top to see what's using memory; then change the sort order with > and <

SpamAssassin Rules Emporium (SARE): http://www.rulesemporium.com/

To learn more about configuring SpamAssassin, run this at the command prompt: perldoc Mail::SpamAssassin::Conf

Of course visit the SpamAssassin site: http://spamassassin.apache.org/

Visit the SpamAssassin Wiki for more ideas: http://wiki.apache.org/spamassassin/FrontPage

and the Exit0 SpamAssassin Wiki http://www.exit0.us/

This is an example of a /etc/spamassassin/local.cf file:

bayes_path /var/lib/amavis/.spamassassin/bayes auto_whitelist_path /var/lib/amavis/.spamassassin/auto-whitelist lock_method flock # # We need stuff from these senders, and they tend to get marked as spam. # We want to whitelist our close business partners. # We subscribe to industry specific newsletters and whitelist them also. # Later we manually feed these to Bayes as ham. whitelist_from spambin@example.com whitelist_from *@generalmotors.com whitelist_from *.usanewstoday.com # # We need stuff from autonetamerica and the Lottery and it always gets marked as spam. # So we will create custom rules that let these particular subject lines reduce the score. header AUTONETAMERICA Subject =~ /Auto Net America/ score AUTONETAMERICA -5.000 header YOURLOTTERY Subject =~ /Your Lottery Results!/ score YOURLOTTERY -5.000 # # We change the scores on a few standard tests score RAZOR2_CF_RANGE_51_100 0.500 score URIBL_WS_SURBL 2.000 score URIBL_PH_SURBL 2.500 score RCVD_IN_SORBS_HTTP 1.000 score RCVD_IN_SBL 1.000 score RCVD_IN_NJABL_PROXY 1.000 score RCVD_IN_SORBS_MISC 0.500 score RCVD_IN_BL_SPAMCOP_NET 2.000 score RCVD_IN_NJABL_SPAM 2.200 score HTML_WEB_BUGS 1.500 # # use_auto_whitelist 0 # uncomment to disable auto-whitelist - a number of people recommend NOT using auto-whitelist.

Make sure you run spamassassin --lint after adding any new rules.

Normally, SpamAssassin is set up as a multi user system and users are able to tweak their own personal settings by editing their individual user_prefs file. In our case the only users that use SpamAssassin are amavis and root. The /etc/spamassassin/local.cf file is used to configure SpamAssassin site wide but in our case, editing /var/lib/amavis/.spamassassin/user_prefs would have a similar effect. However, certain global SpamAssassin settings will have no effect if placed in user_prefs, therefore you only need to maintain local.cf.

If image spam is a problem for you, please see another one of my documents that attempts to address that issue. This type of spam is particularly dangerous because it tries very hard to corrupt your Bayes database:


****************************************************** Use the Rescue CD: Index ****************************************************** Boot up using the etch CD, answer the first few prompts (Language, Country, Keyboard), let it discover devices (but go no further!), then use [Alt]+F2 to open a console. At this point you can mount your hard drive and repair GRUB or LILO (and perform other tasks). Here is how I used the rescue CD to repair LILO after a disk clone using Ghost 2003. You MUST know in advance which partition is your root partition. You should keep a copy of the text in /etc/fstab to refer to. In this example we will assume the root partition was mounted on /dev/hda6, a separate /boot partition was mounted on /dev/hda1 and you are repairing LILO. If you use other mount points (like /var for example) (depending on what you are trying to repair) you may need to mount those too. To repair LILO: mkdir /hardroot mount /dev/hda6 /hardroot chroot /hardroot If you have a separate boot partition, this would need to be mounted too: mount /dev/hda1 /boot cp /etc/lilo.conf /etc/lilo.conf-original /sbin/lilo

Use [Ctrl][Alt][Del] to reboot. I got a bunch of errors when I ran 'lilo', but it booted up just fine. Once it reboots you should run:

shutdown -r -F now

To repair GRUB, you would instead run this command (edit as needed to reflect the type of disk you are using):

/sbin/grub-install /dev/hda


****************************************************** Links, FAQs and such: Index ****************************************************** debian http://www.debian.org postfix http://www.postfix.org amavisd-new http://www.ijs.si/software/amavisd/ SpamAssassin http://www.spamassassin.org Razor http://razor.sourceforge.net DCC http://www.rhyolite.com/anti-spam/dcc/ Pyzor http://pyzor.sourceforge.net ClamAV http://www.clamav.net

Similar Documents (for other distributions): http://www.geekcomix.com/cgi-bin/classnotes/wiki.pl?Setting_Up_An_Anti-SPAM_Gateway http://www.flakshack.com/anti-spam/ http://www.freespamfilter.org/ http://ezine.daemonnews.org/200309/postfix-spamassassin.html http://freshmeat.net/articles/view/857/ http://www.gentoo.org/doc/en/mailfilter-guide.xml?style=printable http://www.novell.com/coolsolutions/feature/16093.html

Other Debian documents that also include local mail delivery: http://workaround.org/articles/ispmail-sarge/ http://www.fatofthelan.com/articles/articles.php?pid=22 http://www.falkotimme.com/howtos/perfect_setup_debian_sarge/index.php

Would you like a web based interface for per-user settings and quarantine control? Don't install this on a production machine until you are comfortable with it and keep in mind that the quarantined email is stored in a MySQL database on this machine which means you need a disk partition large enough to hold it. This software is not without issues and installing and configuring Maia Mailguard is not trivial so I suggest you read through the documentation and mailing list archives. http://www.renaissoft.com/projects/maia/index.php http://www.renaissoft.com/pipermail/maia-users/ http://www.linuxjournal.com/article/7427 If you are interested, this will help you get it installed: http://www200.pair.com/mecham/spam/debian-maia.html

Email testing tools: http://www.declude.com/Articles.asp?ID=100 http://zmailer.org/mxverify.html http://www.gfi.com/emailsecuritytest/ http://dnsreport.com/ and http://www.dnsstuff.com/ http://www.eicar.org/anti_virus_test_file.htm http://www.webmail.us/testvirus http://rbls.org/ http://spamlinks.net/tools-relay.htm#web

apt-get and dpkg: http://oat.tao.ca/node/view/141 http://www.knoppix.net/forum/viewtopic.php?t=2638 http://jaqque.sbih.org/kplug/apt-pinning.html http://www.debian.org/doc/manuals/apt-howto/ http://newbiedoc.sourceforge.net/tutorials/apt-get-intro/info.html.en http://www.oreilly.com/catalog/linuxnut4/chapter/ch05.pdf

neat way to upgrade only 'stable' packages: http://www.freespamfilter.org/forum/viewtopic.php?t=265

iptables: http://iptables-tutorial.frozentux.net/iptables-tutorial.html http://www.cites.uiuc.edu/wsg/talks/iptables/iptables-rh8.rules.txt http://www.hackinglinuxexposed.com/articles/20030703.html http://www.justlinux.com/nhf/Security/IPtables_Basics.html http://huizen.dto.tudelft.nl/devries/security/iptables_example.html http://morizot.net/firewall/gen/

DNS based spam databases (RBLs): http://www.declude.com/junkmail/support/ip4r.htm

UTF-8 http://www.lugod.org/mailinglists/archives/vox-tech/2003-06/msg00128.html

Postfix: http://www.postfix.org/BASIC_CONFIGURATION_README.html http://www.postfix.org/STANDARD_CONFIGURATION_README.html http://www.stahl.bau.tu-bs.de/~hildeb/postfix/ http://www.postfix-book.com/debugging.html http://www.informatik.uni-bonn.de/pub/software/postfix/addon.html http://www.metaconsultancy.com/whitepapers/smtp.htm http://mywebpages.comcast.net/mkettler/sa/SA-rules-howto.txt http://www.mines.edu/academic/computer/spamuserprefs.shtml http://www.securitysage.com/antispam/ http://www.postfix.org/uce.html http://jimsun.linxnet.com/misc/postfix-anti-UCE.txt http://www.geekounet.org/filters/header_checks http://www.fredshack.com/docs/postfix.html

Security: http://www.debian.org/doc/manuals/securing-debian-howto/ http://linuxgazette.net/issue89/gonzales.html http://www.acm.org/crossroads/xrds6-1/linuxsec.html http://www.tldp.org/HOWTO/Security-HOWTO/index.html http://www.freefire.org/lib/hardening.en.php3

Linux: http://linux.about.com/library/bl/open/newbie/blnewbie_toc.htm http://loll.sourceforge.net/linux/links/index.html http://www.fifi.org/cgi-bin/man2html http://wireless.ictp.trieste.it/school_2002/lectures/fonda/MoreLinux/rute/node1.html

Cron: http://www.unixgeeks.org/security/newbie/unix/cron-1.html http://www.pantz.org/os/linux/programs/cron.shtml

AIDE: http://linuxgazette.net/issue75/maiorano.html http://www.gnu.org/directory/aide.html

Debian: http://articles.linmagau.org/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=158&page=1 http://www.debianplanet.org/index.php?or=7 http://newbiedoc.sourceforge.net/ http://www.debian.org/distrib/packages http://www.desktop-linux.net/debian-rclocal.htm http://www.backports.org http://www.falkotimme.com/howtos/index.php

Amavisd-new and SpamAssassin: http://wiki.apache.org/spamassassin/FrontPage http://www.exit0.us/ http://www.rulesemporium.com/index.html http://wiki.apache.org/spamassassin/CustomRulesets http://www.ijs.si/software/amavisd/#faq-spam http://sourceforge.net/mailarchive/forum.php?forum=amavis-user http://news.gmane.org/gmane.mail.spam.spamassassin.general http://www.surbl.org/

Spam Links: http://spamlinks.net/

Regular Expressions (Regex): http://www.regular-expressions.info http://www.silverstones.com/thebat/Regex.html#intro http://gmckinney.info/resources/regex.pdf http://www.contactor.se/~dast/mail2sms/regex.shtml http://www.quanetic.com/regex.php http://www.koralsoft.com/regextester/ http://www.renatomancuso.com/software/pcreworkbench/pcreworkbench.htm

Disk Cloning: http://service1.symantec.com/SUPPORT/ghost.nsf/docid/2001111413481325?Open&src=&docid=19 http://www.rajeevnet.com/hacks_hints/os_clone/os_cloning.html http://service1.symantec.com/SUPPORT/ghost.nsf/docid/2000042113083825?Open&src=&docid=1999021909463125

Populating relay_recipient_maps: http://www2.origogeneris.com:4000/relay_recipients.html http://www-personal.umich.edu/~malth/gaptuning/postfix/ http://www.unixwiz.net/techtips/postfix-exchange-users.html http://postfix.state-of-mind.de/patrick.koetter/mailrelay/

Using eDirectory to provide real-time userid pass/fail to Postfix using OpenLDAP: http://www.novell.com/coolsolutions/gwmag/features/trenches/tr_postfix_gw.html

Configuration files quick reference:

/etc/aliases /etc/postfix/main.cf /etc/postfix/master.cf /etc/postfix/sender_access /etc/postfix/transport /etc/postfix/virtual /etc/postfix/relay_recipients /etc/postfix/body_checks /etc/postfix/header_checks /etc/amavis/amavisd.conf /var/lib/amavis/.spamassassin/user_prefs /etc/spamassassin/local.cf /var/lib/amavis/.razor/razor-agent.conf /etc/clamav/clamd.conf /etc/apt/preferences /etc/apt/sources.list

A few unmentioned commands and FAQs:

How do I tell how much space is left on the drive? Answer: df

How do I tell how my hard drive is partitioned? fdisk -l /dev/hda or /dev/sda

How do I delete just one email that is in the queue? Answer: first run "mailq" and note the ID number. Then run postsuper -d <ID number>

I'm still in the testing stages of this box and I have a bunch of test messages in the queue that I want to delete, how do I do this? Answer: postsuper -d ALL deferred This will delete messages in the deferred queue.

I would like to change the IP address of this box, how do I do this?. Stop Postfix and amavisd-new. Look in these files, and edit as needed: /etc/network/interfaces /etc/hosts /etc/networks /etc/resolv.conf /etc/postfix/main.cf possibly /etc/postfix/sender_access Run "postmap /etc/postfix/sender_access" possibly /etc/postfix/transport Run "postmap /etc/postfix/transport" possibly /etc/spamassassin/local.cf Modify your firewall settings, and send the iptables commands. reboot Modify other computers' hosts file(s) as needed. Change PuTTY to the new address If you find more places to change, let me know,

I want to insure postmaster and abuse @example.com receives mail even if it is spam, how do I do that? Set: @spam_lovers_maps = ( ['postmaster@example.com', 'abuse@example.com'], );

How do I bypass scanning for some senders or recipients? http://www200.pair.com/mecham/spam/bypassing.html

I want to have my Exchange box send its mail out through the spamfilter, so I can further isolate it from the Internet. See these posts: http://www.freespamfilter.org/forum/viewtopic.php?t=82 http://marc.theaimsgroup.com/?l=amavis-user&m=113415019700881

The post above also explains how to use altermime to attach a disclaimer to outgoing mail (mail that is sent from the Exchange server).

spam traffic and load

Some final comments:

Spam traffic is increasing dramatically. About 90% of the email that passes through my system is spam. Setting this system up won't be the end of your anti-spam project, I'm afraid. You'll catch a LOT of spam with this, but some will keep getting through, and some good email will get blocked. You'll learn and tweak things as you go forward.

I hope this doc is useful to you. Feel free to contact me, mr88talent at yahoo dot com, with comments and suggestions or corrections. This website was created for my own personal use and entertainment.

Everyone is welcome to copy all or any portion of this document for their own use and/or to share with others pretty much as they see fit, provided it is done so without malicious intent and you do not claim that you wrote this document.

P2 750mhz 512mb

whole system uses around 1.5GB out of 15GB. amavis servers 2 LOAD 50% CPU, 80MB of ram, 5,000-8,000 spam emails a day(varies by day), 4,000 users.(2500 banned accounts through relay recipiants) Amavis servers 4 LOAD 80% CPU, 40-50mb per amavis instance, 5,400 emails a day+, 4,500 email accounts. With this old machine, our harddrive speed became a problem. After 8 months on uninterapted work, server hdd started to slow down, and it was replaced by faster server.

p5 3.5Ghz 512

new system uses 926 Mb amavis servers 6 LOAD 14-54% CPU, amavis uses 10% memory per one, 10,000 spam emails a day, 4500 users.(2600 banned accounts through relay recipiants)

More Anti-Spam

Here are restrictions that get huge amount of spam to go away. This is taken out, out of final main.cf of postfix, used at a company that receives 35,000 spam email a day.

#spam phase3 
smtpd_recipient_restrictions =
        check_client_access hash:/etc/postfix/access,
        #next 3 Are checking for fully-qualified name 
        #deselect next to enable revere dns
        reject_rbl_client relays.ordb.org,
        reject_rbl_client rbl.maps.vix.com,
        reject_rbl_client sbl.spamhaus.org,
        reject_rbl_client bl.sorbs.netelays.ordb.org,
        reject_rbl_client cbl.abuseat.org,
        reject_rbl_client dul.dnsbl.sorbs.net,
        reject_rbl_client bl.spamcop.net,
        reject_rbl_client relays.mail-abuse.org

****************************************************** Disclaimer: Index ******************************************************

This website was created for the author's personal use and entertainment. There is absolutely no warranty. Use entirely at your own risk.

Any information contained herein is freely available elsewhere and simply reinterpreted, or more likely misinterpreted, and cannot be assumed to be accurate. There are mistakes in this website and there may or may not be any effort to correct those mistakes in the future.

The author accepts no responsibility for any loss or damage caused by the use, lack of use, or misuse, of information contained in this website.

Where links are provided to other websites, the author accepts no responsibility and shall not be liable, either directly or indirectly for the content, legality, accuracy, reliability, suitability, quality or decency of content, information, product, advice or services provided by and contained in those sites.

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MyWiki: DebianAntiSpamGatewayEmailServer (last edited 2014-08-11 13:44:30 by LukaszSzybalski)