A Java vulnerability has caused at least 600,000 Macs worldwide to become infected by the Flashback Trojan without the user's knowledge or consent. Mac users must patch their OS and take other appropriate actions as described below to secure their computers.
Please also treat this as a wakeup call that, contrary to popular belief, malware impacts Macs as well as PCs. Be very wary of offers to install software and addons from unknown sources.
Apple has made patches for OS X available through Apple's Software Update. To download and install the necessary patches, please follow the steps below as soon as is practicable:
If you do not have administrator access to your Mac, contact your ITC immediately to install the patch.
If you are running an older OS X operating system, please make the time to upgrade to a newer version of the OS as soon as possible. In the meantime, you can protect yourself by either disabling Java in your web browser (in Safari, it’s a Security preference), or by turning it off using the Java Preferences application, which can be found in the Utilities folder in Applications. Be aware that this may impact some functionality that uses Java.
You'll find more information at Quick protection for older Macs from the Flashback trojan