Cybersecurity researchers have uncovered a Remote Access Trojan (RAT), that’s been flying under antivirus programs’ radars for at least half a year and targeting, at least, education institutions. As reported by Ars Technica, the RAT’s been dubbed SysJoker by researchers from Intezer who discovered it. When they first discovered it, on a Linux-based Webserver belonging to a “leading educational institution”, they learned it was written from scratch.
They don’t know who built it, when they built it, or how they distribute it. Their best guess is that it was built in the second half of last year, by an advanced threat actor with “significant resources”. They came to this conclusion knowing the fact that fully cross-platform malware, with four separate C2 servers, are a rare sight.
As for the distribution, they speculate that the educational institution in question installed it on its endpoint through a malicious npm package. They are confident the attackers did not exploit any flaws in the target’s systems, but rather tricked somebody into installing it. There’s a good chance the attackers aren’t casting a wide net, but are rather engaged in “ espionage together with lateral movement which might also lead to a ransomware attack as one of the next stages,” against specific targets.
The malware is written in C++, and is yet to be added to the VirusTotal malware search engine. It also seems to be quite potent, as it can create files, add registry commands, install further malware, run commands on the infected device, or even shut itself off.
As the RAT is yet to be added to the virus database, system administrators who discover the infection need to remove the malware manually. According to iTechPost, that’s a three-step process: 1) eliminate the malware’s persistence mechanism, manually delete all the affected files and kill all the malware-related programs; 2) run a memory scanner to ensure all malicious files have been removed; 3) check if all software tools are updated, tighten up firewall settings, and investigate possible access points.