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Trojanized installers of the Telegram messaging application are being used to distribute the Windows-based Purple Fox backdoor on compromised systems.

That’s according to new research published by Minerva Labs, describing the attack as different from intrusions that typically take advantage of legitimate software for dropping malicious payloads.

“This threat actor was able to leave most parts of the attack under the radar by separating the attack into several small files, most of which had very low detection rates by [antivirus] engines, with the final stage leading to Purple Fox rootkit infection,” researcher Natalie Zargarov said.

First discovered in 2018, Purple Fox comes with rootkit capabilities that allow the malware to be planted beyond the reach of security solutions and evade detection. A March 2021 report from Guardicore detailed its worm-like propagation feature, enabling the backdoor to spread more rapidly.

Then in October 2021, Trend Micro researchers uncovered a .NET implant dubbed FoxSocket deployed in conjunction with Purple Fox that takes advantage of WebSockets to contact its command-and-control (C2) servers for a more secure means of establishing communications.

“The rootkit capabilities of Purple Fox make it more capable of carrying out its objectives in a stealthier manner,” the researchers noted. “They allow Purple Fox to persist on affected systems as well as deliver further payloads to affected systems.”

images from Hacker News