Powerful New Linux Malware Shikitega Uses Unusual Multi-Stage Stealth

Here's a warning from the threat intelligence unit of AT&T Cybersecurity, AT&T Alien Labs: With a rise of nearly 650% in malware and ransomware for Linux this year, reaching an all-time high in the first half year of 2022, threat actors find servers, endpoints and IoT devices based on Linux operating systems more and more valuable and find new ways to deliver their malicious payloads. New malwares like BotenaGo and EnemyBot are examples of how malware writers rapidly incorporate recently discovered vulnerabilities to find new victims and increase their reach. But they've discovered a new malware targetting Linux endpoints and IoT devices, stealthily "delivered in a multistage infection chain where each module responds to a part of the payload and downloads and executes the next one. An attacker can gain full control of the system, in addition to the cryptocurrency miner that will be executed and set to persist."

The Register summarizes their report: The malware was dubbed "Shikitega" for its extensive use of the popular Shikata Ga Nai polymorphic encoder, which allows the malware to "mutate" its code to avoid detection. Shikitega alters its code each time it runs through one of several decoding loops that AT&T said each deliver multiple attacks, beginning with an ELF file that's just 370 bytes... AT&T didn't say how the initial infection occurs, but it did say Shikitega exploits two Linux vulnerabilities disclosed in 2021 to achieve its ultimate objective, which AT&T said appears to be the installation and execution of the XMRig cryptocurrency miner. The final stage also establishes persistence, which Shikitega does by downloading and executing five shell scripts that configure a pair of cron jobs for the current user and a pair for the root user using crontab, which it can also install if not available. Shikitega also uses cloud hosting solutions to store parts of its payload, which it further uses to obfuscate itself by contacting via IP address instead of domain name....> >

Bottom line: Shikitega is a nasty piece of code. AT&T recommends Linux endpoint and IoT device managers keep security patches installed, keep EDR software up to date and make regular backups of essential systems.

Ars Technica reports: The ultimate objective of the malware isn't clear. It drops the XMRig software for mining the Monero cryptocurrency, so stealthy cryptojacking is one possibility. But Shikitega also downloads and executes a powerful Metasploit package known as Mettle, which bundles capabilities including webcam control, credential stealing, and multiple reverse shells into a package that runs on everything from "the smallest embedded Linux targets to big iron." Mettle's inclusion leaves open the potential that surreptitious Monero mining isn't the sole function....

The unknown threat actors responsible for the stealth of the malware are likely to have found a way to sneak it onto some systems.