Apple has released “Flashback malware removal tool” which removes the most common variants of the Flashback malware.
If the Flashback malware is found, a dialog will be presented notifying the user that malware was removed. In some cases, the Flashback malware removal tool may need to restart your computer in order to completely remove the Flashback malware.
This update is recommended for all OS X Lion users without Java installed.
See http://support.apple.com/kb/HT5246 for more details about this update.
See http://support.apple.com/kb/HT1222/ for information about the security content of this update.
More info and download link (356 KB) here.