…………….. let’s look closely at the facts around the Flashback Trojan causing all this consternation, and clear up what it is versus what it is not, and put the results of the incident in perspective.

Yes it’s true that some 600,000 Macs are confirmed to have been infected. The claim, first made by Dr. Web, an outfit I had never heard of, has since been corroborated by Kaspersky Labs, whose research and analysis capabilities are well-respected. More than half of the compromised machines are in the U.S., 95,000 in Canada, 47,000 in the U.K., and 41,000 in Australia.

The trojan targets a vulnerability in software that is not even an Apple product: Java. You’ll recall that Java is add-on software created by Sun Microsystems and now the property of the software giant Oracle. Rather common, it is no longer shipped as a default add-on to Apple’s Mac OS X beginning in 2011, when Apple first shipped Lion.

Through this hole in Java, certain Web sites are serving up malicious Java applets. Once inserted on the machine, the software then prompts the user to enter the password they use to run the machine. It attempts to trick the user by appearing as an update to Adobe’s Flash video and animation software.

If the user doesn’t fall for the trick, it tries something else. Here again it checks to see if there are any Microsoft Office applications on the machine, or Skype. If there are, it deletes itself.

Then it does something interesting. It scans the contents of the Mac’s hard drive to determine if certain applications are present, and if they are, it deletes itself. Among those applications are security tools such as Little Snitch, a networking security tool, or Packet Peeper, another security tool. It also deletes itself if it sees the user has installed XCode Mac developers tools, and any kind of anti-virus software.

Presuming it finds none of them, it proceeds to contact a command-and-control server for the purpose of downloading and installing more malware. That malware is being used to commandeer the Macs and generate Web traffic to boost revenue for some pay-per-click ads on Web sites, making money for someone who’s behind the scheme. Nothing surprising there.

Apple has issued a fix to Mac OS X that closes the hole in Java, and you can protect yourself by running Software Update from within your machine’s System Preferences. Today would be a good day to do that if you haven’t already. Once you’ve done this you’re no longer vulnerable to the attack.

If you’re among the 600,000 already compromised you can turn to third parties to help you remove it. F-Secure has some instructions here for determining if your machine is affected. If you’re comfortable running some commands in the Mac’s terminal program, there are also some good instructions here at ArsTechnica.

So what does all this say about the state of security on the Mac? Nothing that wasn’t true already. No system is perfectly secure, and this, along with MacDefender, amounts to exactly the second security incident worth mentioning to hit the Mac in about a year. The number of machines affected is less than 1 percent of the 63 million Macs currently in use around the world.

The conventional wisdom has often held that Macs are targeted by malware less often than Windows machines because of their relatively small market share. This still has some merit, but the fact is that Windows is also where the vulnerabilities are. Historically, Mac OS X has been substantially less vulnerable to this sort of thing than Windows.

Does that let Apple off the hook entirely? No, though to its credit, Apple had a fix ready within a week of learning of this vulnerability. That’s not exactly a pokey response, especially when the problem lies not directly within Apple’s software, but in Oracle’s.

via What’s This? A Mac Virus? No Actually It’s a Weakness in Java. – Arik Hesseldahl – News – AllThingsD.