The security measures only just put in place by Apple in response to the attack.that's been plaguing Apple's Mac platform for the last few weeks has been updated by its creators, to bypass
The new iteration of the nasty bug is called MacGuard, and was discovered by Mac security company Intego. Unlike the previous version, it doesn't require an administrator password to install itself.
The malware works by directing users to dodgy sites through manipulation of Google's search algorithms. These sites automatically download MacGuard into the Mac Applications folder.
Previous versions of the malware required the user to enter an administrator password before they'd install, and Apple made a point of telling users not to enter these passwords if any nasty software tried to install itself.
It's possible that MacGuard's creators updated their nasty program on purpose to take advantage of Apple's warning -- having read the advice on Apple's website, Mac users may feel safe because this new malware doesn't ask for an admin password.
Once installed, MacGuard pops up scary-looking porn sites and generates fake virus alerts, convincing users their Macs are infected by all sorts of loathsome viruses. It then prompts users to enter credit card information and buy a subscription to eliminate the viruses. If you pay, the fake alerts stop, so you think you've won. But really you've just given your credit card info to some shady customers.
Apple's been slow to respond to its first real Mac attack, and the fact that the authors of the nasty malware have been so quick to respond suggests Apple's got a fight on its hands. Until now the Mac platform has been relatively free of viruses -- that could change, though, if other malware authors start to up their game.
Apple's planning an update to Mac OS X that it says will automatically find and remove Mac Defender and its known variants. We'll have to wait and see whether that squashes the bug.
If you've downloaded the malware by mistake, follow the steps on Apple's support page.