A recent version of malicious software called Flashback exploits a security flaw in Java in order to install itself on Macs.   Apple has released software updates for systems running OS X Lion and Mac OS X v10.6 that will update Java to fix the security flaw, and remove the Flashback malware if it is present.  For Macs running Mac OS X v10.5 or earlier, you can better protect yourself from this malware by disabling Java in your web browser(s) preferences.

In a sign of Apple’s increasing vulnerability to attacks, some Mac computers belonging to Apple employees were infected with Java-related malware when the employees visited a software development website.

Apple admitted its systems were penetrated by hackers. In the wake of this attack Apple released the update to its Java package for Mac computers that can remove the most common variants of the Flashback malware.

The Apple hacks happened when vulnerability in Java, from Oracle Corp., allowed hackers access to core computing systems, but the same vulnerability may also put regular PC users at risk.  A similar Java related exploit against Facebook was revealed Friday.