I haven't come across a virus since I have been owning a Mac. But I do take precautions such as running Norton 11 for Mac. They also have the beta of NOD32 that works out well. Once in a while I would get internet attacks while using the school wifi. Regardless, if you stay updated with the SL service packs, you'd be all set.
as macs get more popular, more and more viruses will be created. recently there has been a small bump in the amount of malicious files on there since the user base has grown. before it was considered virus-free since who wants to make malicious files for an OS that only a niche market used. (even though viruses STILL did exist and still do on Macs) windows was targeted primarily for its amounts of users. you gotta try really hard to get a virus on there.
