I have not had a virus on any of the Macs I have owned since the 90s. There was the Flashback Trojan just a couple of weeks ago, but testing sites came out promptly where one could test their Mac and fix it if it was infected. Also, Apple updated their OS in response, too. Other than that...nothing. I am using a freebie virus scanner right now, ClamXAV. Not sure how robust it is.