Apple has released a new update for its OS X operating system that fixes the Flashback malware update that has supposedly affected more than 600,000 machines.

"This Java security update removes the most common variants of the Flashback malware," say the software notes for the update hitting Apple computers on Thursday night.

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"This update also configures the Java web plug-in to disable the automatic execution of Java applets. Users may re-enable automatic execution of Java applets using the Java Preferences application. If the Java web plug-in detects that no applets have been run for an extended period of time it will again disable Java applets. This update is recommended for all Mac users with Java installed."

Users can get the 66MB update via the automatic update tool in OS X or Apple's website.