See that chart there? That's a lovely graphic conjured up by Sophos, a company that makes ends meet by offering anti-virus software. The company just so happens to also have a flavor for OS X, and based on data culled from 150,000 users, it looks as if 50,000 machines had at least one piece of malware onboard. 'Course, a sizable chunk of these listed (Mal/ASFDldr-A and Mal/Conficker-A, for example) won't even run on OS X, so having them on one's HDD does little more than take up a section of space that could otherwise be used to archive a digital image of Aunt Mary. Graham Cluley, senior technology consultant at Sophos, even stated that Sophos doesn't "see as much Mac malware as Windows malware... by a long shot," but given that its Mac edition software is totally free, you might as well give it a look if you're suddenly stricken with paranoia.