Oh, and this may have the newest version of malware- bios flashers!
http://hackaday.com/2009/03/23/bios-level-malware/
What would this mean? It can attack Mac OS, Vista, XP, Linux and almost any kind of other OS's.
It also would be impossible to remove from the computer because it would be flashed and locked.
I hate to continue the nerdiness, but without root access (or physical access) these types of attacks are impossible. Which anybody employing the most basic type of computer security should be protected from. (don't let strangers use your computer, and password protect access to it)
Sure there have been mac viruses, but the risk is much lower. Also it really helps when the maker of your computer regularly offers security updates, and listens to reports they receive about vulnerabilities.
But now that I think about it, BYC is probably not the correct forum to have this debate. The bottom line is everyone should make sure they have the most up to date anti-virus, and even more important
back up your data, back it up often, and just for safe measure back it up one more time. of course if you have a mac and an extra hard drive Time Machine is already doing that for you.