While malware has long been an almost daily annoyance for Windows PCs, Mac users have become accustomed to not worrying about malicious software. Threats arise from time to time—in January of this year, for example, a Trojan horse made the rounds in pirated copies of Apple’s iWork software—but most Mac users these days are probably running without virus protection software. Apple’s encouraged that, too, by frequently touting the Mac’s resistance to malware in its advertising materials, especially when compared to Windows. But with the release of Mac OS X Snow Leopard, Apple’s finally decided to subtly step up its game when it comes to malware, much as it has done in the past with phishing in Safari. For the first time, the Mac OS contains a built-in system that detects malicious software and attempts to protect users from inadvertently damaging their computers.