Underscoring the growing sophistication of Mac-based malware, a trojan preying on OS X users has adopted several stealth techniques since it was discovered last month.
Updates to the Flashback trojan, which gets installed by disguising itself as an Adobe Flash update, now prevent the malware from running on Macs that use VMware Fusion. Such virtual machine software is routinely used by security researchers to test the behavior of a malware sample because it's easier to delete a virtual instance when they're finished than it is to wipe the hard drive clean and reinstall the operating system.
According to MAC Security Blog:-Updates to the Flashback trojan, which gets installed by disguising itself as an Adobe Flash update, now prevent the malware from running on Macs that use VMware Fusion. Such virtual machine software is routinely used by security researchers to test the behavior of a malware sample because it's easier to delete a virtual instance when they're finished than it is to wipe the hard drive clean and reinstall the operating system.
The latest version, Flashback.D, has gotten a bit sneakier. First, it checks to see if the user is running Mac OS X in VMware Fusion. If so, it does not execute. It does this because many malware researchers test malware in virtual machines, rather than infect full installations, as it is easier to delete them and start over with clean copies. This means that security researchers analyzing and looking for this malware need to be running regular Macs.
Next, the installer for the malware downloads the payload when running the postinstall script.
Next, the installer for the malware downloads the payload when running the postinstall script.
Finally, it no longer installs the easy-to-spot ~/Library/Preferences/Preferences.dylib. Instead, it installs the backdoor inside Safari, and does so in two ways. It adds information to Safari’s info.plist file, with the location of the backdoor, and it adds the actual backdoor module at /Applications/Safari.app/Contents/Resources/UnHackMeBuild.
Even if a user removes the above file (UnHackMeBuild), they need to edit Safari’s info.plist file; if not, Safari will look for the backdoor on launch, and, if it is not found, Safari will quit.
-News Source (Intego Blog, The Register)
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