Sophos Labs releases free antivirus for Mac
Fortunately, there are now plenty of good antivirus options for Mac users to combat the rising number of threats. The most recent addition to the mix is Sophos, which has just released the totally free Sophos Antivirus Home Edition. All the features you'd expect from a good antivirus app are there -- like realtime protection, heuristics (the ability to detect new threats for which Sophos does not have definitions), autorun defense, and quarantining.
Sophos has been a respected name in the security business for quite some time, and you certainly can't complain about the price.
Download Sophos Antivirus Home Edition for Mac