Here’s some news for you:
Mac OS X is, and always has been, vulnerable to trojans.
The whole point of trojans is that they exploit the most serious security problem of all: gullible users. A trojan does not take advantage of any holes in the code, all it needs is to persuade someone to click an “OK”, or to run an installer, and it has done its job.
The problem with a lot of the reporting of malware, especially by traditional media, is that the word “virus” is widely used to mean “malware”.
Most of us who are half-way to computer literate know the difference between a trojan and a virus, but most of the rest of the world has no idea.
That’s why we’re seeing news articles about “Mac viruses”, and we shall continue to see them in future. That’s also why your Windows-using friends are going to be smirking at you, saying: “Heh. And you said you didn’t get viruses on your Mac. Bet you feel stupid now, huh?”
Any computer is vulnerable to trojans. The security hole they exploit is not in the operating system, it’s the one sitting in the chair and tapping on the keyboard.
Wanna keep your computer clean? Next time you’re surfing some random porn site and a pop-up tells you to “Install a codec” so you can watch the movies, it’s a good idea to click Cancel.