I don't use a Mac but noticed these reports this morning
http://macscan.securemac.com/boonana-trojan-horse-discovered/#more-111
http://www.intego.com/news/trojan-horse-os-x-koobface-a-affects-mac-os-x.asp
Worrying if Macs and Linux are now going to become bigger targets for malware. If the London Stock Exchange does switch to Linux there will certainly be the incentive to start targeting non-windows systems :(
More on it here, you still have to accept the applet for it to run, boonana and koobface are one in the same, just different names for the same Trojan, no OS is ever completely safe. http://www.theregister.co.uk/2010/10/27/koobface_for_mac/
"Mac users should be aware that this threat exists, and that it is likely to be operative in the future, so this Koobface Trojan horse may become an issue for Macs."
For that to happen, attackers will probably have to figure out how to bypass a window OS X prominently displays warning that a self-signed Java applet is requesting access to the computer. Assuming they do, or are able to trick users into clicking "Allow" anyway, they will also need to resolve issues preventing the downloaded files from installing.
Those are high hurdles. But Koobface's considerable success on Windows shows just how gullible many marks are when it comes to scams promising free videos"
I think LSE are already on Linux, considering their recent reports of a huge decrease in transaction times from the move.
Linux is a big target, but the methods are usually different. Windows is for end users, and so the method there is to trick that end user or rely on their gullibility. Here we get loads of attacks -- on Linux -- but due to the fact they are workstations almost all the attacks are direct, namely brute force methods on the root password, but since root logins are disabled anyway this is fairly hopeless.