Wisniewski reminded Snow Leopard users that they can probably upgrade to Mountain Lion, which of course will receive security updates. And even in the absence of any future patches, their current OS will continue to work.

"But the best way to stop an attack is to patch the vulnerability," Wisniewski added.

Apple did not reply to questions about whether Snow Leopard will continue to receive security updates, and if so, for how long.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at , on or subscribe to . His email address is .

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