Big Head: New Ransomware Targeting Widows Users With Fake Updates and Installers

A new ransomware strain was recently discovered by security researchers and is said to be distributed through a malvertising campaign which promotes fake Windows updates and Microsoft Word installers.

The ransomware dubbed ‘’Big Head’’ was first discovered by security researchers at FortiGuard Labs and later Trend Micro published a report in which it claimed that both the previously identified variants as well as a third variant was the work of a single threat actor.

The ransomware which features .Net binary has the ability to deploy AES-encrypted files on the victim’s system: first one (1.exe) is used to propagate the malware, second one (archive.exe) is used to communicate with the threat actor’s Telegram channel and third one (Xarch.exe) displays a bogus Windows update.

Similar to other ransomware, it performs several checks and inspections to decide whether to execute or self-terminate. Before executing file encryption, the ransomware checks if its running in a virtual environment, deletes recovery backup, terminates processes, and avoids directories that can expose its presence.

Moreover, the malware’s capability includes disabling the Task Manager to prevent the victim from terminating or investigating its activities. It also uses its self-terminating techniques is the user’s machine language matches the country code of Russian, Belarusian, Ukrainian, Kazakh, Kyrgyz, Armenian, Georgian, Tatar, and Uzbek.

Two more variants of Big Head were identified by Trend Micro. The second Big Head variant has both ransomware and info-stealer capabilities. It exfiltrates various sensitive data from the user’s system including product keys, list of directories and running processes, browsing history, operating network, and helps capture screenshots.

The third variant includes a file infector identified as Neshta which infects the target’s machine by inserting a malicious code into executable files. Usage of this technique can disguise the threat as a virus, thus making it difficult for security solutions to detect the ransomware.

The threat actor behind the ransomware remains unknown, however, researchers at Trend Micro speculate it to have Indonesian origins based on the YouTube name which is a phrase in Bahasa. Moreover, the researchers have also issued a security warning keeping in mind the multi-faceted nature of the ransomware.