Another big difference between Mac and PC is the level of security you can expect from viruses and other unwanted intrusions. Because the vast majority of the world's computers run Microsoft Windows, most attacks focus on PCs. Malware like Trojans, which trick users into installing them by pretending to be something desirable, like antivirus programs, and botnets, which quietly enlist computers into an army of zombie machines designed to distribute spam or advertise fraud, are now common threats to PCs, but rarely harm Macs.
This doesn't mean that Mac users should completely ignore security. Recently, a Trojan known variously as Mac Protector, Mac Defender and MacGuard has been showing up on Apple machines. A window claiming to be the "Apple Security Center" pops up and indicates that it has found viruses on the computer. It then prompts the user to download Mac Protector, a cleverly disguised piece of software intended to steal your credit card information. As Macs become more popular and begin to claim a larger market share, these threats will inevitably increase. However, as one observer puts it, "a Mac owner who runs no security software is vastly less likely to be the victim of a successful attack than a Windows user who's protected up to his eyeballs" [source: McCracken].