The best antivirus for mac is to not use/uninstall IE and MS office from your mac. Thats it unless you are on a cross-platform netwrok. There are plenty of other options than using these things even if you've converted recently from pc to mac. The only reason a virus will be on and affect a mac is if you have a MS produced software installed since certain virii can attack MS macros and whatever else MS has decided not to fix in their programming. As of the present (and forseeable future) OS X does not have a native virus and neither does unix.