Newsflash: Macs do have security vulnerabilities. While people who understand how viruses and malware work have understood this for ages, Mac vulnerabilities became big news as the Flashback malware tore through the Apple community. At its peak, Flashback and its variants had infected an estimated 1 percent of the worldwide Mac population.
This one was a particularly nasty wake-up call known as a drive-by download, as it required only that you go to a Web page to become infected. Apple malware could be unusually lucrative for malware makers because Apple owners have been told implicitly for years that Macs don't get malware, so they're not expecting infections. There's no easy solution to this, so it's recommended that if you own a Mac, you get yourself a security suite -- especially one that plugs vulnerabilities in third-party software such as the one that exposed Macs to Flashback.
For more on this story, see our FAQ on Flashback.