For almost three decades now, the conventional wisdom about Macs and viruses has been simple: They don't get them. Viruses are made for PCs, they say, which means Macs aren't vulnerable to them. And whenever the latest virus scare goes cycling through the PC world, my fellow Mac users and I can relax, if not outright throw our heads back and laugh.
That may be about to change.
If Macs don't get many viruses, it's not because they're magically or systemically immune; it's because virus coders usually target the bullseye, the most vulnerable, most populous demographic, in order to give their viruses the widest spread. Historically, that's meant targeting Windows, which in the past, has had not only many more vulnerabilities, but a much wider audience.
However, two key trends are on the move right now. One, PC users are migrating to Windows 7, which is intrinsically much stronger than its predecessors. Two, OS X is starting to capture a wider and wider market share. Those two factors combined may, very soon, make OS X a more appealing target for coders who want to do harm.
Of course, in no way does that mean "jump ship." What it means is "be proactive, and be ready." Outfit your Mac with a professional-caliber virus security program, if you haven't already, and surf the Web carefully and responsibly. All the usual rules of thumb for minimizing risk still apply; stay away from the Internet's bad neighborhoods, don't open spam (especially not attachments), block pop-ups except from sites you trust, and so on.
PC users have dealt with virus threats since the days of floppy disks and dial-up. Should the need arise, Mac users can too.