Filtering Spam with Procmail
Pages: 1, 2

I'd also like to show how to configure spam bouncer. Since I tested both of these programs on a single-user machine, I removed the lines from my .procmailrc that I had added to configure junkfilter before I installed spam bouncer. I then became the superuser and proceeded with the build:

su
Password:
cd /usr/ports/mail/spambnc
make install clean
exit

Related Reading Programming Internet Email By David Wood Table of Contents Index Sample Chapter Full Description

At the very end of this build, you'll receive a message telling you that the rules were installed into /usr/local/share/spambnc and that you should read /usr/local/share/doc/spambnc/documentation.html. Unlike junkfilter, spam bouncer doesn't have a global configuration file; instead, you add configuration options to your .procmailrc. You really should read that suggested documentation file to see which options are available to you as I won't cover them all here.

I found that spam bouncer had a few additional filtering features that I liked. For example, by default, it will filter out all emails written in Chinese, Japanese, Korean, Russian and Turkish. If you don't use these languages, any correspondence in them will probably be spam. However, if you happen to use one of those languages, don't forget to change the default "no" to "yes" for your particular language so spam bouncer won't filter out all of your email.

If you want to be more aggressive in your filtering of spam, you can configure spam bouncer to check a variety of Internet sites that keep lists of known spammers and relays. By default, these checks are turned off. Before enabling these checks, visit the relevant sites to ensure they are still in operation and to register if it is required. The sites listed are:

• dorkslayers
• MAPS (Mail Abuse Prevention System) Dial-up User List
• ORBZ (Open Relay Blackhole Zones)
• The Open Relay Database
• OsiruSoft's Open Relay Spam Stopper
• The Spamhaus Project

Even if you decide to leave these checks off, the mentioned sites do contain interesting reading.

To configure spam bouncer, you'll have to add these two lines to your .procmailrc to tell procmail to call spam bouncer:

SBDIR=/usr/local/share/spambnc
INCLUDERC=${SBDIR}/sb.rc

Note that the INCLUDERC line should be the very last line in your variable section, meaning it should be just before your own filtering recipes.

You'll also need to tell spam bouncer where to put the messages it filters out. The spam bouncer utility has two variables for this: the first tells it where to put messages that might be spam, and the second tells it where to put messages that are pretty well guaranteed to be spam. I set up my two variables like this:

BLOCKFOLDER=$MAILDIR/garbage
SPAMFOLDER=$MAILDIR/spam

and placed them just before the INCLUDERC line.

Once you've set those four required variables, spam bouncer is ready to roll. There are several dozen other variables I haven't mentioned that might pique your interest enough to include in your own .procmailrc file; see that documentation file for details.

If you're subscribed to any mailing lists, you'll soon find that some mailing lists are caught and flagged by spam bouncer, while others survive the spam bouncer checks and make it to your own filtering recipes. For example, all the mail from the freebsd questions list was being placed in my garbage folder instead of my questions folder, yet the messages from most (not all) of the securityfocus mailing lists made it to my security folder.

To tell spam bouncer not to filter a message just because it came from a mailing list, create a file in your home directory called legitlists. In that file, put the address of each mailing list you're subscribed to on one line; mine looks like this:

questions@freebsd.org
freebsd-questions@freebsd.org
security@freebsd.org
advocacy@freebsd.org
newbies@freebsd.org
sectools@securityfocus.com
newsscan@newsscan.com

After about a week or so of adding rogue lists to this file as you discover them, you shouldn't have any more trouble with mailing lists messages being blocked just because they came from a mailing list. However, virii and spam sent to those mailing lists will continue to be filtered out, which is probably what you were aiming for.

Another file you may want to create in your home directory is called .nobounce. If you have friends that send email from known spammer domains such as hotmail.com, put their addresses in this file, one address per line. This will tell spam bouncer that you trust that particular email address to not send you any spam.

I hope the last two articles helped to get you started on the possibilities of using procmail. If you want additional information on either junkfilter or spam bouncer, check out their related Web sites:

• junkfilter
• spam bouncer

In the next article, I'll let you in on the results of my latest tour through the ports collection.

Dru Lavigne is a network and systems administrator, IT instructor, author and international speaker. She has over a decade of experience administering and teaching Netware, Microsoft, Cisco, Checkpoint, SCO, Solaris, Linux, and BSD systems. A prolific author, she pens the popular FreeBSD Basics column for O'Reilly and is author of BSD Hacks and The Best of FreeBSD Basics.

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