New Krasue Linux RAT targets telecom companies in Thailand

A previously undetected Linux RAT dubbed Krasue has been observed targeting telecom companies in Thailand.

Group-IB researchers discovered a previously undetected Linux remote access trojan called Krasue has been employed in attacks aimed at telecom companies in Thailand.

The Krasue Remote Access Trojan (RAT) has remained undetected since at least 2021 when it was registered on Virustotal. The name “Krasue,” comes from the Thai name of a nocturnal native spirit known throughout Southeast Asian folklore.

The experts have yet to determine the initial infection vector and the scale of the campaign.

Threat actors could propagate the threat by exploiting vulnerabilities in Internet-facing systems, conducting credential brute force attacks, and tricking victims into downloading deceptive packages or binaries (i.e., files masquerading as product updates) from untrustworthy third-party sources.

The malware is equipped with seven embedded rootkits to target different Linux kernel versions. The Krasue’s rootkit is based on three open-source LKM rootkits, Diamorphine, Suterusu, and Rooty

The Krasue malware is deployed during the later stages of an attack chain, it allows attackers to maintain persistence.

The experts speculate the RAT is likely to either be deployed as part of a botnet or sold by initial access brokers.

“The rootkit can hook the `kill()` syscall, network-related functions, and file listing operations in order to hide its activities and evade detection.” reads the report published by Group-IB. “During the initialization phase, the rootkit conceals its own presence. It then proceeds to hook the `kill()` syscall, network-related functions and file listing operations, thereby obscuring its activities and evading detection.”

Krasue relies o RTSP (Real Time Streaming Protocol) messages to serve as a disguised ‘alive ping.’ This tactic is uncommon in the threat landscape.

The researchers observed multiple similarities between the Krasue rootkits and the Linux XorDdos, another Linux malware.

Researchers speculate Krasue was likely developed by the same author of XorDdos.

“While the primary components of the Krasue Remote Access Trojan differ from XorDdos, there are substantial and unique overlaps in the rootkit segment.” concludes the report.

“The information available is not enough to put forward a conclusive attribution as to the creator of Krasue, or the groups that are leveraging it in the wild, but the fact that these malicious programs are able to remain under the radar for extended periods makes it clear that continuous vigilance and better security measures are necessary.”

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Pierluigi Paganini

(SecurityAffairs – hacking, rootkit)