Apple's update was offered only to customers running Snow Leopard; Macs powered by the older Mac OS X 10.5, known as Leopard, will not receive the same anti-MacDefender protections.
Mac users can manually from the Apple site, or install it using the operating system's integrated update service.
After Tuesday's update, Snow Leopard detects Mac scareware and warns the user to dump the file in the Trash. (Image: Sophos)
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at or subscribe to . His e-mail address is .
in Computerworld's Security Topic Center.