The infamous Flashback malware has successfully infected over half a million Mac computers according to Russian security firm Doctor Web (Dr.Web).
Dr.Web reported on 4 April that the BackDoor.Flashback.39 had infected far more computers than researchers initially thought.
Nearly 300 are thought to be inside Apple's headquarters.
"Now BackDoor.Flashback botnet encompasses more than 550,000 infected machines, most of which are located in the United States and Canada," said Dr.Web in an initial statement.
The figure has since increased, with Dr.Web malware analyst Sorokin Ivan claiming on Twitter that the count has risen to 600,000.
@mikko, at this moment botnet Flashback over 600k, include 274 bots from Cupertino and special for you Mikko - 285 from Finland— Sorokin Ivan (@hexminer) April 4, 2012
The newest version of the Flashback Trojan is believed to have been active since 2011. The malware targeted an unpatched Java vulnerability within Apple's Mac operating system.
The malware reportedly exploited the vulnerability to allow an applet to operate outside of the Java security sandbox, granting hackers the ability to remotely install code on a targeted system.
Apple patched the vulnerability on 4 April, issuing an OS X update designed to fix the problem. Specifically the company said that its Java for OS X 2012-001 and 10.6 Update 7 releases address 12 separate vulnerabilities in the OS X version of the Java platform.
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