600,000 Macs Worldwide Reportedly Infected by Flashback Trojan

Ars Technica reports on a Tweet from Russian malware analyst Ivan Sorokin at Dr. Web claiming that the Flashback trojan has now infected over 600,000 Macs worldwide. That number reportedly includes 274 machines "from Cupertino", presumably meaning at Apple's headquarters.

According to Dr. Web, the 57 percent of the infected Macs are located in the US and 20 percent are in Canada. Like older versions of the malware, the latest Flashback variant searches an infected Mac for a number of antivirus applications before generating a list of botnet control servers and beginning the process of checking in with them.

The authors of the Flashback trojan have continued to tweak the software since it first surfaced last September, adjusting its tactics several times to include both social engineering tricks and exploits of vulnerabilities.

The most recently-seen version of Flashback surfaced earlier this week, exploiting a Java vulnerability that was unpatched on OS X. While Oracle had released an update closing the hole on Windows back in February, Apple had yet to issue a fix for Macs, as the company has historically maintained its own Java updates that are deployed some time after Oracle issues its own corresponding updates. But just a day after that report, Apple did update Java to address the vulnerability being exploited by Flashback.

Antivirus firm F-Secure has instructions on how users can determine whether their machines are infected by the Flashback trojan. The instructions do involve running commands in Terminal, and users should thus take care to follow the instructions exactly.