Up until now Mac owners have been relatively safe (and smug) when it came to the infectability of their computers. Worms, trojans, viruses, and other malware were considered to be primarily the domain of Windows. That may have changed last week, however, when the Russian security company, Dr. Web, reported that as many as a half a million Macs are already infected with what is being called the “Flashback Trojan”. Here’s how to know if you have Flashback Trojan, and how to get rid of Flashback Trojan.

The “Security Alert” trojan, sometimes known as a ‘rogue antivirus’ attack, is making the rounds again. First spotted a few years ago, until recently the “web security” antivirus alert trojan targeted mainly PCs, tricking Windows users into downloading the evil ‘BestAntivirus2011.exe’ file by telling them that “To help protect your computer Windows web security have detected trojans and ready to remove them.” (Note the poor language usage.) Now this same tactic is being used to attack Mac users – all that has changed is the “Windows” to “Apple” and the file name (‘MacProtector.mpkg for Macs’) – even the poor language remains the same! “To help protect your computer Apple web security have detected trojans and ready to remove them.” says the pop-up. Don’t fall for it, and whatever you do, don’t click on “Remove all”, which will cause the malware to be downloaded to your computer.

Two years ago, almost to the day, a Spanish airliner belonging to Spanair crashed just after takeoff. Of the 172 people on board, 154 were killed. New information now reveals that one of the airplane’s central computer systems was infected with malware, and that the crash was likely directly attributable to this malware infection.

A devious new method of getting unsuspecting users to download Trojan malware to their computers takes the form of a fake parking ticket placed on their car’s windshield. The ticket, reading “PARKING VIOLATION This vehicle is in violation of standard parking regulations,” contains a web address to download a “toolbar” to view images of the car that is the subject of the “ticket”. Of course, the ‘toolbar’ isn’t really a toolbar at all – it’s the Trojan.

A new computer worm called Downadup – also known as the Conficker worm – is spreading like wildfire across personal computers, even though it has only been on the scene for a relatively short time. First spotted just weeks ago, in November, the Downadup worm is estimated to already be resident on at least 3 1/2 million PCs.

A nasty new Windows ransom trojan called Ransom-A (also Troj/Ransom-A and TROJ_RANSOM.A) freezes your computer, and if you don’t pay it ransom money, it starts deleting your files.