Cybersecurity researchers have uncovered a new Linux rootkit called PUMAKIT that comes with capabilities to escalate privileges, hide files and directories, and conceal itself from system tools, while simultaneously evading detection.
“PUMAKIT is a sophisticated loadable kernel module (LKM) rootkit that employs advanced stealth mechanisms to hide its presence and maintain communication with command-and-control servers,” Elastic Security Lab researchers Remco Sprooten and Ruben Groenewoud said in a technical report published Thursday.
The company’s analysis comes from artifacts uploaded to the VirusTotal malware scanning platform earlier this September.
The internals of the malware is based on a multi-stage architecture that comprises a dropper component named “cron,” two memory-resident executables (“/memfd:tgt” and “/memfd:wpn”), an LKM rootkit (“puma.ko”), and a shared object (SO) userland rootkit called Kitsune (“lib64/libs.so”).
It also uses the internal Linux function tracer (ftrace) to hook into as many as 18 different system calls and various kernel functions such as “prepare_creds,” and “commit_creds” to alter core system behaviors and accomplish its goals.
“Through its staged deployment, the LKM rootkit ensures it only activates when specific conditions, such as secure boot checks or kernel symbol availability, are met. These conditions are verified by scanning the Linux kernel, and all necessary files are embedded as ELF binaries within the dropper.”
“PUMAKIT is a complex and stealthy threat that uses advanced techniques like syscall hooking, memory-resident execution, and unique privilege escalation methods. Its multi-architectural design highlights the growing sophistication of malware targeting Linux systems,” the researchers concluded
