For a long time, Mac users were quick to point out that few, if any viruses were even made for Mac. Well, with the popularity of iOS and Mac systems in general, it appears the age of no malware for Macs might be coming to an end.
The Flashback trojan has purportedly already infected 500,000 Mac computers and without remedy, is poised to get many more.
The problem is, amongst others, that since viruses mostly don't exist for Mac, most Mac users don't have any form of anti-virus.
In the original SlashGear post, there's a link to F-secure with details on how to test your Mac to see if it's infected.