I have found that Avira has a free anti-virus for Linux. I was wondering if there were any more free anti-virus programs for Linux.

i though linux didn't need it?

I don't know the current state of viruses in linux. about five or so years ago there was one.... ONE ... active virus in the wild that was specific to the linux kernel, and it was harmless.

As linux becomes more popular, we *will* have more linux viruses, and we will need (and have) better AV software on linux.

However, it seems like most AV software running on linux is not to fight linux virus - it is to fight windows virus. We mount windows drives on linux machines and clean them up using anti-windows-virus software that runs on linux. We also boot infected windows boxes with a linux live cd, and run AV on linux to clean up the infected windows machine.

That is good to know. I have Ubuntu on one hard drive and XP on another. I switch back and forth between them. I know Linux doesn't need to be defragged but curious about the window cleaning in Linux. I used to use windows cleaner for the cookies, history and files like that. Linux has a place to delete history.

Well, ClamAV has been around quite a while, kapersky has a linux version, as does AVG.

Linux is rarely susceptible to viruses as such, it's more common to get 'rooted', i.e. have a new, hidden login that gives root access.
This is most common if you don't keep up with security patches.

chkrootkit and rootkit hunter are useful to check for rootkits.

Tripwire is a rootkit preventative, but does take a little work to properly set up.

Malware on Linux is a whole different beast compared to its counterpart in Windows.

The good news is that it's much harder to get a Linux computer infected.

The bad news is that when that happens, it's usually *much* worse.