2004 and 2006
A few years after the release of OS X, 2004 brought a new shell script worm called Renepo. The worm’s main goal was to disable Mac OS X’s firewall and security settings. It also installed tools for password-sniffing and made key system directories world-writeable, undetected. The worm was only spread when Macs connected to other Macs and not via the Internet, however. Leap-A, a virus discovered in 2006 was a different story however – spreading via OS X’s iChat messaging application. Disguised as an image file, the Trojan propagated through victims’ contact lists and infected Cocoa applications on each machine.