“After gaining access to users’ contact lists, Gen:Variant.Downloader.167 distributes itself through Facebook’s instant messaging and Yahoo Messenger from one friend to another,” states Catalin Cosoi, Chief Security Strategist at Bitdefender. “Besides being wonderfully polite, the Trojan also uses biblical verses as decryption keys for its data.”
It starts when users receive a polite question from a Facebook or Yahoo Messenger friend whose system has been infected with the malware. “I want to post these pictures on Facebook, do you think it’s OK?,” the malicious messages read. To add legitimacy, the URLs following the question belong to storage services Dropbox and Fileswap, frequently used for sharing pictures and files.
The malware is then executed on the machine, where it creates a folder with a random name and an “.exe” extension. It also shows a message box during the installation process.
“This application is not compatible with the version of Windows you're running,” the message reads. “Check your computer's system information to see whether you need an x86 (32-bit) or x64 (64-bit) version of the program, and then contact the software publisher.” The downloader can restart and update itself.
In May 2013, a similar piece of malware infected thousands of Facebook users worldwide. The Dorkbot malware posed as a “jpg” image but was actually an executable file, capable of spying browser activities and stealing personal data. Another scam promised naked videos of Facebook friends but dropped a Trojan instead.