I read a few reviews of the new iantivirus by PC Tools. I tested it out on my work machine and it was surprisingly light on resources and incredibly easy to use. I know everyone usually recommends ClamXAV but I tried that and I didn't like how it didn't run real time, took forever to scan, etc. I know, I know, Macs don't get viruses, blah blah blah, I don't care. It never hurts to be too safe.