Description

Security experts have analyzed Two instances of the 'Big Head' ransomware strain, which may be propagating via malvertising that advertises false Windows updates and Microsoft Word installs. The 'Big Head' ransomware is a.NET program that installs three AES-encrypted files on the target system: one to propagate the malware, another for Telegram bot communication, and the third to encrypt data and display a bogus Windows update to the user. When executed, the ransomware creates a registry autorun key, overwrites existing files, if necessary, changes system file properties, and disables the Task Manager. Each victim is given a unique ID, which is either taken from the%appdata%ID directory or created using a random 40-character string. Before encrypting the targeted files and attaching a ".poop" extension to their filenames, the ransomware deletes shadow copies to prevent easy system restoration. During the encryption process, the ransomware presents a screen that seems to be a genuine Windows update. Following the completion of the encryption procedure, the following ransom is placed on various folders, and the victim's wallpaper is also modified to warn of the infection. The second edition retains ransomware capabilities while also including stealth behavior, including functionalities for collecting and exfiltrating sensitive data from the target machine. This version of Big Head can steal browsing history, directory lists, installed drivers, running processes, product keys, and active networks, as well as screenshots. The third variation includes a file infector known as "Neshta," which inserts malicious code into executables on the compromised machine and attempts to avoid detection using signature-based procedures. Notably, this edition differs from the previous two in terms of ransom letter and wallpaper, but it is still linked to the same threat actor.