As the recent news on malware on Mac shows, Windows users aren't the only targets for unscrupulous people. Once market share increases to a certain level, users on any platform start getting attention from malicious software developers. Of course, the same goes for us Linux users. We're not as "immune" as many like to think.
While there's no real hurry to protect ourselves, it's best we start arming ourselves by knowing what out options are at this point. If ever the need arises, at least we'll know where to look for the tools we need. Thankfully, Linux developers in general have been strengthening security a bit at a time over the years, so it's no easy task even if there were attempts to infect Linux systems with malware.
Here's a few options I know. This isn't an exhaustive list, but it's a start.
ClamAV - The open source antivirus solution. I've tried this years ago, but don't use it. I find it too slow for my liking but it's an option for those who insist on a pure open source setup.
BitDefender for Unices - There's a free version of this available. I use this as my main tool for disinfecting Windows machines that got some serious infections that can't easily be removed from inside Windows. It works well for Windows and should work for Linux as well. Files are files, afterall.
Avast! Linux Home Edition - Another good antivirus. I have this installed on my LiveUSB as well. I don't use it as often but it's still a good alternative to BitDefender.
FProt - I've used this for a short time years ago. It's quite good although I find it's console-based interface rather inconvenient. For those who'd like to be able to automate things away with scripts this, along with BitDefender, is a nice option.
Kaspersky Rescue CD - If you don't fancy installing antivirus software on your machine, there's always bootable CD options out there. Kaspersky is probably the best option here though I find Kaspersky's update servers rather wanting.
Avira Rescue System - Same as Kaspersky Rescue CD, Avira has a bootable CD image that you can burn to a disc. Just boot from the CD, update and scan. Simple. Avira does tend to behave rather paranoid though, so I'd use this more as a last option.
If Linux does eventually have a breakthrough in the desktop like its supporters have claimed for years and years, every year then it's likely that malware will start appearing with frequency on the Linux desktop. Best be prepared with the necessary knowledge when time comes.