"Here is an excellent article summarizing the current state of affairs regarding the Flashback Trojan." Jim Hamm goes on to comment, "As the use of Macs becomes more widespread in the computer world, I suspect, unfortunately, there may be more malware attempts in the future on the Mac. One big concern I have is why Apple is so slow to respond to threats like this, as the article points out?"
The article does state that "Apple has been introducing a series of technologies—tools like Address Space Layout Randomization (ASLR), sandboxing, and DEP—to reduce the chances of exploitation even when a Mac is vulnerable and to limit the potential damage of an attack. But these technologies aren’t perfect, especially when complex programs that run Web content like Java or Adobe Flash are involved.
"Gatekeeper will significantly change the game for manually installed Trojans when it’s released later this year; it will make that form of attack much less profitable (and thus less likely)."