This tutorial describes how to scan emails for image spam with FuzzyOCR on a Fedora 12 server. FuzzyOCR is a plugin for SpamAssassin which is aimed at unsolicited bulk mail containing images as the main content carrier. Using different methods, it analyzes the content and properties of images to distinguish between normal mails (ham) and spam mails.

This tutorial describes how to scan emails for image spam with FuzzyOCR on an Ubuntu 9.10 server. FuzzyOCR is a plugin for SpamAssassin which is aimed at unsolicited bulk mail containing images as the main content carrier. Using different methods, it analyzes the content and properties of images to distinguish between normal mails (ham) and spam mails.

There is currently a lot of spam where the spam "information" is attached as .pdf or .xls files, sometime also hidden inside a .zip file. While these spam mails are not easy to catch with e.g. SpamAssassin or a Bayes filter, the ClamAV virus scanner can catch them easily when it is fed with the correct signatures as ClamAV is built to scan mail attachments.

Apache SpamAssassin is an extensible email filter that is used to identify spam. Once identified, the mail can then be optionally tagged as spam for later filtering. It provides a command line tool to perform filtering, a client-server system to filter large volumes of mail, and Mail::SpamAssassin, a set of Perl modules allowing Apache SpamAssassin to be used in a wide variety of email systems.

Estimates say that spam makes now up for 80 - 90% of all emails, and many mail servers have difficulties in managing the additional load caused by the latest spam, and spam filters such as SpamAssassin do not recognize large parts of that spam as they did before.

Groupware setups like Zarafa often leave the spam scanning to external tools – but still has to sort the tagged mails. This article shows two ways of sorting and filtering tagged spam mails in Zarafa.

"I run a Postfix-based mail server that services a few hundred users with an average load of a couple of thousand legitimate messages a day -- but thanks to spam, the actual load on the server is much higher. I use Realtime Blackhole Lists (RBL) and Distributed Checksum Clearinghouse (DCC) clients on Postfix and SpamAssassin to reduce the impact of spam."

"Current Spam fighting techniques like for example SpamAssassin are reactive. SpamAssassin uses a rule based approach and a Bayesian filter.[...]Bayesian filtering requires to collect a rather large amount of mail messages before messages can be filtered. This illustrates that reactive Spam fighting is no real solution."

This guide explains how to install Maia Mailguard, a spam and virus management system, on a Debian Lenny mailserver. Maia Mailguard is a web-based interface and management system based on the popular amavisd-new email scanner and SpamAssassin.