The notorious Mac Defender malware is once again leaving OS X systems vulnerable to infection.
Security vendor Intego reported that a new version of the malware package is able to bypass Apple's latest security update.
"Just a few hours after Apple released a security update to block the Mac Defender fake anti-virus, a new variant has been found which tests Apple's ability to rapidly respond to new threats," Intego said in a security alert.
"The latest version comes in an installer package named mdinstall.pkg, and installs an application named MacGuard, which is the latest name that has been used for this malware."
Apple released an update earlier this week to activate a security protection tool in Mac OS X 10.6 which allowed systems to detect and isolate currently known versions of the 'scareware' application.
With the latest variant of the malware, however, Mac users are once again presented with fake security warnings and attempts to convince them to pay for non-existent protection software.
Paul Ferguson, senior threat researcher at Trend Micro, told V3.co.uk that the update could indicate the beginning of a "one-upmanship" game, which malware writers and security companies have played in the PC space for years.
Ferguson also believes that Mac OS will be just one of several platforms to enter the crosshairs of malware writers.
"It is a multi-platform problem now. You will also notice that Android seems to have a target on its back," he said. "The criminals are going where the money is, whether it's Mac, Android, PC or whatever."
New Vikendi map adds snow, snowmobiles and new aural and visual twists
Faults and bad weather ground SpaceX, Blue Origin, Arianespace and United Alliance
New regulation expected to cut greenhouse gas emissions by about 17 million metric tonnes between 2020 and 2050
Molybdenum ditelluride is a two-dimensional material that can be easily stacked into multiple layers to create a memory cell