Many Mac users might believe that Mac OSX does not contain viruses, that is not entirely true, to be honest there isn't a single OS without one virus. Though it is true OSX hardly contains any viruses compared to Windows. But one thing is for sure is that not many people have anti-virus software for their Macintosh's because just like many other users they believe that the chances of them getting a virus is really low. The number of viruses grows all the time, so Sophos an anti-virus software company brought out a free Mac anti-virus software just for the Mac. This is actually a full featured program, which eliminates viruses and also has protection of the same level as many businesses. If you haven't already I recommend you guys check this piece of software

Here is the link for more information: Sophos- Macintosh Anti-Virus