September 7, 2022

AT&T researchers have discovered a new Linux malware that can bypass multi-stage deployment. The malware known as Shiketega can bypass antivirus by using a polymorphic encoder that makes static signature-based detection impossible.

Shiketega’s method of infection remains unknown, but researchers at AT&T said the malware uses a multi-stage infection chain in which each layer delivers only a few hundred bytes, activating a simple module and moving it to the next.

The malware has diverse capabilities, including exploiting vulnerabilities to increase its privileges, adding persistence to the host via crontab, and finally introducing a cryptocurrency miner oh infected devices.

“Using the encoder, the malware runs through several decode loops, where one loop decodes the next layer until the final shellcode payload is decoded and executed. The encoder stud is generated based on dynamic instruction substitution and dynamic block ordering. In addition, registers are selected dynamically,” the AT&T report states.

Once the decryption is complete, the shellcode is executed to contact the malware’s command and control servers (C2) and receive additional shellcode commands that are stored and executed directly from memory.

To further reduce the chances of being discovered, the actors behind Shikitega use legitimate cloud hosting services to host their command-and-control infrastructure.

The sources for this piece include an article in BleepingComputer.