You'll need to turn back the clock more than a few laps in order to remember Patient Zero. In 2004, it was one of the first bugs for Mac OS X to gain any real degree of notoriety, mostly for being Apple-related at a time when such things simply did not happen. The malware authors used the Mac's hidden file extensions to camouflage their executable file, which was made to look like something else entirely -- usually an MP3. Once the user clicked the icon, the Trojan could commit all sorts of antisocial behavior, such as deleting files, spreading the infection within the machine, and sometimes invading the email software so it could go visit the host's friends. But the bug was presented as a sample of what could happen, and there's no indication that it ever made it into the wild.