The question of whether the average Mac user needs to install anti-malware software has been, for years, the subject of intense debate among industry authorities and pundits. Most Mac experts I know say it's unnecessary — and indeed a waste of time, money, and CPU cycles — unless your employer or some legal constraint requires you to install such software or you participate in high-risk computing (as described in the previous section).
Nevertheless, it's a tricky question to answer because there's so little Mac malware in the wild right now but no logical reason there couldn't be more (and worse) malware out there in the future. If the day comes when a nasty virus starts spreading rapidly among the world's Macs, it could very well be the paranoid and overcautious among us who escape unscathed, while the experts curse themselves for their carelessness. On the other hand, that day may never come, and in the meantime, you'll be spending money on annual software upgrades, waiting for disk scans to complete, and cluttering up your Mac with something that may have no real-world effect on your security.
My professional opinion, after working in the Mac world for more than 15 years and after considerable study and contemplation, is that almost everyone can protect themselves from almost every potential malware threat by adopting the following common-sense habits:
Use a NAT gateway. If you connect directly to the Internet, by which I mean your Mac ...