The threat actor(s) behind many Dridex and Locky campaigns have been using a new Remote Access Trojan (RAT), Proofpoint security researchers warn.
Known as TA505, the attackers have been using malware dubbed tRat, which was written in Delphi and is modular in nature. The new piece of malware was first spotted at the end of September, when it was being spread by an unattributed actor. Malicious Word documents used in the attack used macros to download the RAT.
The malware was picked up by TA505 last month and used in an attack on October 11, as part of an email campaign that used both Microsoft Word and Microsoft Publisher files for distribution purposes. The attack targeted users at commercial banking institutions.
tRat, the security researchers say, achieves persistence by copying the binary to a directory in the AppData folder. Next, it creates a LNK file in the Startup directory to ensure the binary is executed when the system starts.
The malware uses TCP port 80 for command and control (C&C) communications, encrypting data and transmitting it hex-encoded. The initial network request sent to the server includes system information such as computer name, system username, and tRat bot ID.
“Currently, we believe that the only supported command in the loader is “MODULE,” which contains at least a module name and export name,” the security researchers reveal.
TA505 has historically engaged into high-volume, high-frequency, sophisticated campaigns, and has been known to test new malware including BackNet, Cobalt Strike, Marap, Dreamsmasher, and even the Bart ransomware, though they never returned to distributing any of these.
“However, we observe these new strains carefully as they have also adopted new malware like Locky or less widely distributed malware like FlawedAmmyy at scale following similar tests. Moreover, their adoption of RATs this year mirrors a broader shift towards loaders, stealers, and other malware designed to reside on devices and provide long-term returns on investment to threat actors,” Proofpoint concludes.