Cybersecurity researchers have identified PUMAKIT, a sophisticated Linux rootkit that utilizes advanced stealth techniques to evade detection and compromise systems. Discovered through artifacts uploaded to VirusTotal in September 2024, PUMAKIT employs a multi-stage architecture and innovative methods to manipulate system behaviors while remaining hidden. It represents a significant escalation in the complexity of malware targeting Linux environments.
At its core, PUMAKIT functions as a Loadable Kernel Module (LKM) rootkit, allowing it to integrate deeply into the Linux kernel. It consists of multiple components, including a dropper named cron, memory-resident executables (/memfd:tgt and /memfd:wpn), the kernel rootkit puma.ko, and a shared object (SO) userland rootkit named Kitsune (lib64/libs.so). The dropper ensures stealthy deployment by embedding essential files as ELF binaries, which only activate when specific conditions—such as kernel symbol availability or secure boot checks—are met.
PUMAKIT achieves its stealth through various techniques, including hooking into 18 system calls and kernel functions like prepare_creds and commit_creds to escalate privileges and conceal its presence. The malware also employs Linux’s function tracer (ftrace) to modify core system operations. Memory-resident execution of its components minimizes on-disk footprint, further enhancing its ability to evade detection. Unique methods, such as using the rmdir() syscall for privilege escalation, underscore its innovative approach to maintaining persistence and control.
Although PUMAKIT has not been attributed to a specific threat actor, its sophisticated design highlights the growing capabilities of malware targeting Linux systems. Elastic Security Lab researchers noted that every stage of its infection chain is carefully constructed to ensure stealth and effectiveness. With its combination of syscall hooking, multi-stage deployment, and privilege escalation techniques, PUMAKIT serves as a stark reminder of the evolving threat landscape in Linux security.
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