New malware brings together the strength of ransomware and a botnet in one attack, researchers said.
Called Virobot, the attack not only encrypts files on infected machines, but it also converts a system into a spam botnet and leverages it to spread itself to other victims, said researchers at Trend Micro.
Researchers first found the malware September 17. Virobot checks compromised machines for the presence of specific registry keys to determine if the system should be encrypted.
The ransomware uses a cryptographic Random Number Generator to generate the encryption and decryption key, which is then sent along with machine-gathered data to the command and control (C&C) server via POST.
For encryption, the malware targets file types such as .txt, .docx, .xlsx, .pptx, .jpg, .png, .csv, .sql, .mdb, .php, .asp, .xml, .psd, .odt, and .html.
Once the encryption process has been completed, the malware displays a ransom note and a ransom screen. The ransom note is written in French, but the malware is currently affecting users in the United States, Trend Micro said in a post.
The malware’s server has been taken down, meaning it can no longer encrypt files, as it requires communication with the C&C to do so.
Virobot also includes a keylogging feature, researchers said. Logged key strokes from the infected machine are then sent to the C&C. Once connected to the server, the malware may also download files such as malware binaries, and execute them using PowerShell.
The botnet capabilities Virobot include the use of an infected machine’s Microsoft Outlook to send spam emails to the user’s contact list. The malware sends either a copy of itself or a malicious payload downloaded from the C&C server.