AntiVirus1 on Linux

While Linux users don't care about viruses (sure, there are a couple, but they never actually spread in the wild), there are various reasons you might want to do virus scanning on Linux.

You have lesser operating systems on the desktop, using Linux as a file server.
All the virus spam annoys you.
You find yourself cleaning up other people's computers.
Etc.

Clam AntiVirus

Clam AntiVirus is probably the best open-source AV solution. The virus database is quite good, although new viruses aren't added to the database quite as fast as with most of the commercial scanners.

Most distributions (including fedora.us) have clamav packages available, so your best bet is to just stick with those (not the binaries on the clamav web site).

Amavis

Amavis isn't actually a virus scanner. It is a content filter for mail that happens to know how to run virus scanners.

There are several branches of the Amavis code:

the original shell script version ("amavis")
the first Perl rewrite ("amavis-perl")
the Perl version designed to run as a daemon ("amavisd")
amavisd-new, a largely rewritten and greatly improved amavisd
amavis-ng, a modular rewrite of amavis-perl/amavisd

Of these, amavis-ng has the cleanest code, and it is the easiest to configure. Unfortunately, it does not include hooks for SpamAssassin. For that reason, amavisd-new is probably the best route to take for now.

If you run Red Hat/Fedora, ask Steve for rpms, either for amavis-ng or amavisd-new.

MailScanner

MailScanner is another popular mail filter that can run virus scanners, much like Amavis. Steve doesn't like it though.

OpenAntiVirus

OpenAntiVirus was the first open-source AV available, but it was not (and is not) very popular because the performance wasn't great. (OpenAntiVirus is written in Java.) ClamAV started as a fast scanner using the OpenAntiVirus database, but eventually the project started their own database as well (to keep it more up-to-date).

Sophos

If you need virus scanning on Windows, or you need really good virus scanning on Linux, you might want to consider Sophos.

They sell to businesses (and other organizations) only though, so look elsewhere if you want something for personal use. It's also not a cheap solution. If all that doesn't scare you off, consider talking to a local reseller.

Sophie

Sophie is an open-source daemon that uses the Sophos virus scanning engine (via a shared library included with Sophos).

Trophie

Trophie does the same thing as Sophie, but it uses Trend's library instead of Sophos's.

Others

The above list was largely lifted from the default amavisd-new config file.

If anyone reading this has comments about other virus scanners for Linux, please hit the Edit button and share.