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Researchers smell a cryptomining Chaos RAT targeting Linux systems

A type of cryptomining malware targeting Linux-based systems has added capabilities by incorporating an open source remote access trojan called Chaos RAT with several advanced functions that bad guys can use to control remote operating systems.

Trend Micro security researchers discovered the threat last month. Like earlier, similar versions of the miner that also target Linux operating systems, the code kills competing malware and resources that affect cryptocurrency mining performance.

The newer malware then establishes persistence “by altering /etc/crontab file, a UNIX task scheduler that, in this case, downloads itself every 10 minutes from Pastebin,” wrote Trend Micro researchers David Fiser and Alfredo Oliveira.

After that, it downloads an XMRig miner, a configuration file, another payload that continually kills competing malware, and the Chaos RAT (remote access tool), which is written in Go and has a ton of capabilities including restarting and shutting down the victim’s machine.

Additionally, the open source tool can perform reverse shell on the infected system, take screenshots of the victim’s device, collect info on the operating system, and download, upload or even delete files.

“An interesting trait of the malware family we intercepted is that the address and access token are passed as compilation flags and hardcoded inside the RAT client, replacing any data inside variables from the main code,” the researchers wrote.

They also noted that the main server, used for downloading payloads, appears to be in Russia, while the Chaos RAT connects to another command-and-control server believed to be in Hong Kong.

It’s worth noting that the Russian server has also been used for cloud bulletproof hosting – the infrastructure services provided by other shady characters that criminals can use to launch, and typically hide, their cyberattacks and other illicit activities. According to the Trend Micro researchers, other cybercriminals have used this same hosting service for their attacks on cloud infrastructure, containers and Linux servers.

“On the surface, the incorporation of a RAT into the infection routine of a cryptocurrency mining malware might seem relatively minor,” Fiser and Oliveira said. 

“However, given the tool’s array of functions and the fact that this evolution shows that cloud-based threat actors are still evolving their campaigns, it is important that both organizations and individuals stay extra vigilant when it comes to security,” they continued. ®