Apple scrubs old Leopards of Flashback Trojan infections - Apple News

Apple has released patches that defend users of its older Mac OS X 10.5 Leopard operating system against security threats.
Monday's security fixes help defend Mac users stuck on the two-year-old operating system against assaults by the infamous Flashback Trojan. Users of the newer Snow Leopard (10.6) and Lion (10.7) operating systems received equivalent fixes last month.

Apple's Leopard Flashback Removal Security Update is designed to clean up Macs running the legacy OS which are not yet running an anti-virus package. In addition, the security update disables Safari's Java plugin by default.

Meanwhile Leopard Security Update 2012-003 disables older versions of Adobe Flash Player, encouraging users to get the latest version directly from Adobe's website.
Both updates can be applied via the Software Update feature built into Mac OS X, but will only "take" if the latest version of that particular track of the operating system, Mac OS X Leopard version 10.5.8, has already been applied.
Apple is acting to prevent users of legacy versions of its operating system from harbouring the Flashback Trojan, which tarnished its reputation for security as a result. Such support is unlikely to continue indefinitely and likely to disappear entirely once Apple updates Mac OS X 10.7 Lion