Snow Leopard users: Turn off automatic date and time in System Preferences immediately
When exploited, the NTP flaw can cause buffer overflows that allow remote attackers to execute code on your system.
What this means is that, if you allow date and time to be set automatically by outside servers, you risk having your computer taken over.
This is a critical issue, it's being exploited as we speak, and Apple has not provided the update to Snow Leopard users, only to 10.8/Mountain Lion and above. I strongly doubt Apple will ever get around to issuing an update for Snow Leopard, or they would have already. Chances of that happening are close to zero