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Linux Orbit: Email Filtering: Stopping Viral Attachments with Exim Version 1.0

May 21, 2002, 09:00 (8 Talkback[s])
(Other stories by John Gowin)

[ Thanks to John Gowin for this link. ]

"Email viruses, as a general rule, attack end users with email clients that allow the execution or opening of attached files. The easiest way to stop these types of virus attacks is to filter email with attachments and prevent them from being delivered. This is a bit like swatting flies with a sledgehammer, especially if it inhibits productivity within a network. The convenience of email attachments has been a boon to productivity in the workplace. The inherent insecurity of email attachments has been the bane of the network administrator. So how do you find that middle ground to make both end users and network administrators happy? The first step is to choose a flexible mail transfer agent like Exim that allows complex configuration options and email filtering.

"In this HOWTO, we're going to take a look at using Exim's mail filtering properties to aid you in your quest for a virus free email system. To begin, we'll take a look at some of the basic configuration options for Exim located in the main configuration file /etc/exim.conf. Then we'll show you how to configure Exim to filter attachments based on their file type. We'll also take a look at the email filter file provided for your use at the Exim Web site, and show you how to use it as a template for your network mail filter. We'll then demonstrate how to install the filter, and also show you where to look if it doesn't work properly. Finally, we'll look at keeping up with new email viruses and how to add their file extensions to your filter to keep you mail users safe..."

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