SpamAssassin

Introduction

SpamAssassin (SA) is an intelligent anti-spam package that identifies spam based on heuristics and a scoring system. If it determines that a message is spam, it simply prepends a marker to the subject line, allowing the user to filter the message using his favorite email client.

How it Works

User- and system-defined patterns are matched against the headers and body of the email message. Each sucessful match is assigned a value or score. If, when all patterns have been tested, the score has reached or surpassed the defined threshold, then the message is marked as spam. At NU ECE, this means the message's subject line is prepended with the tag [SPAM?] or [SPAM]. This allows the user to then set up a filter on his mail client (whether that runs on UNIX, MacOS, or Windows is irrelevant) to either delete these messages, or, more-prudently, to automatically move these messages to a separate mailbox folder which the user will later examine and purge. It's important to note that while this package is very good at identifying spam, just like all anti-spam software, it can incorrectly mark non-spam as spam. It is therefore strongly advised that you set up your filters as described above.

Setting it Up

Setting up SA is trivial. We use procmail(1) to run it before any other recipes. If you don't already have a .procmailrc file in your home directory, log into a centrally-supported UNIX host, such as delta.ece.northwestern.edu, and create one. Insert the following lines at the very top:

For both Solaris and Linux systems, use:

LOGFILE=${HOME}/.procmail.log
#
# SpamAssassin spam filter.
# 2005/10/07 PSB
#
:0fw
| /usr/bin/spamc

That's all there is to it. Now all detected spam will be marked and will be highly visible. If you're a UNIX user and would like to have all SA-designated spam automatically quarantined to another mailbox, contact root and you will be sent another simple procmail recipe to append to your .procmailrc file. Windows users may elect to filter their mail directly on the UNIX mail servers as described above, or may filter on their clients using the spam tags described in the section entitled How it Works.

As always, if you have any questions, please contact EECS IT and we'll be glad to help.

Links to More Info

• UNIX manual page: man spamassassin
• SA official web site
• SA web docs
• SA FAQs

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Phone: 847-491-8140 . FAX: 847-491-4455
webmaster@ece.northwestern.edu

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