A Trojan horse aimed at Apple's Mac OS X operating system has appeared, purporting to be screenshots of the company's forthcoming Mac OS X 10.5 "Leopard" operating system. Although the Trojan, dubbed "OSX/LeapA" by antivirus firms, can spread itself via the iChat instant messaging program and damage applications on a Mac OS X computer, unlike many Windows Trojans, it spreads by fooling users into launching it manually, rather than by leveraging security flaws in the operating system.