"Can I Post These Pictures on Facebook?" Polite IM Trojan Asks

Over 1,300 systems got infected with the latest Instant Messaging Trojan, which uses polite social engineering and biblical verses to hide encrypted data, Bitdefender warns. The antivirus software provider spotted an increasing wave of infections in the past week in countries such as the US, the UK, Germany, Canada, France, Denmark, Japan and Romania.

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. Besides being wonderfully polite, the Trojan also hides some of its encrypted data between biblical verses. The data is eventually decrypted with numbers generated by a mathematical processor.

It all starts when users receive a polite question from a Facebook or YM friend whose system got 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 in the installing 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 a x86 (32-bit) or x64 (64-bit) version of the program, and then contact the software publisher.”

The downloader can restart and update itself. Bitdefender blocked the malware, along with less than half of the security solutions listed on Virus Total.

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 grab personal data. Another scam promised naked videos of Facebook friends but dropped a Trojan instead.

Attackers easily coordinate bots from a control and command server. Besides stealing usernames and passwords, botmasters may also order other malware downloads.

This article is based on the technical information provided courtesy of Cosmin TARSICHI, Octavian MINEA and George CABAU, Bitdefender Malware Researchers.

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