Description

A newly discovered Linux rootkit malware, dubbed Pumakit, leverages advanced stealth and privilege escalation techniques to evade detection and compromise systems. This sophisticated malware consists of multiple components, including a dropper, memory-resident executable, a kernel module rootkit, and a userland rootkit. First identified by Elastic Security in a suspicious binary named 'cron' uploaded to VirusTotal on September 4, 2024, Pumakit remains shrouded in mystery regarding its operators and targets. Typically, rootkits like this are used by advanced threat actors to infiltrate critical infrastructure and enterprise systems for espionage, financial theft, and disruptive operations. Pumakit’s infection begins with the 'cron' dropper, which executes payloads entirely in memory. These payloads load the LKM rootkit ('puma.ko') into the kernel and deploy the userland rootkit ('Kitsune SO') to intercept system calls using the 'LD_PRELOAD' mechanism. Targeting Linux kernels below version 5.7, the rootkit exploits the kallsyms_lookup_name() function to manipulate system behavior. It hooks 18 syscalls and kernel functions like prepare_creds and commit_creds to escalate privileges, execute commands, and conceal its presence. The malware can hide files, processes, and logs, while reinitializing hooks if interrupted to maintain persistence. The Kitsune SO user land rootkit extends Pumakit’s stealth by altering user-level tools like ls, ps, and netstat to obscure malicious activities. It also communicates with a command-and-control (C2) server, facilitating attacker control and exfiltration. Furthermore, Elastic Security has published file hashes and YARA rules to help administrators detect and mitigate Pumakit infections.