N. Korean Hackers Use Fake Interviews to Infect Developers with Cross-Platform Malware

Threat actors with ties to North Korea have been observed targeting job seekers in the tech industry to deliver updated versions of known malware families tracked as BeaverTail and InvisibleFerret.

The activity cluster, tracked as CL-STA-0240, is part of a campaign dubbed Contagious Interview that Palo Alto Networks Unit 42 first disclosed in November 2023.

"The threat actor behind CL-STA-0240 contacts software developers through job search platforms by posing as a prospective employer," Unit 42 said in a new report.

"The attackers invite the victim to participate in an online interview, where the threat actor attempts to convince the victim to download and install malware."

The first stage of infection involves the BeaverTail downloader and information stealer that's designed for targeting both Windows and Apple macOS platforms. The malware acts as a conduit for the Python-based InvisibleFerret backdoor.

There is evidence to suggest that the activity remains active despite public disclosure, indicating that the threat actors behind the operation are continuing to taste success by enticing developers into executing malicious code under the pretext of a coding assignment.

Security researcher Patrick Wardle and cybersecurity company Group-IB, in two recent analyses, detailed an attack chain that leveraged fake Windows and maCOS video conferencing applications impersonating MiroTalk and FreeConference.com to infiltrate developer systems with BeaverTail and InvisibleFerret.

What makes it noteworthy is that the bogus application is developed using Qt, which supports cross-compilation for both Windows and macOS. The Qt-based version of BeaverTail is capable of stealing browser passwords and harvesting data from several cryptocurrency wallets.

BeaverTail, besides exfiltrating the data to an adversary-controlled server, is equipped to download and execute the InvisibleFerret backdoor, which includes two components of its own -

• A main payload that enables fingerprinting of the infected host, remote control, keylogging, data exfiltration, and downloading of AnyDesk
• A browser stealer that collects browser credentials and credit card information

"North Korean threat actors are known to conduct financial crimes for funds to support the DPRK regime," Unit 42 said. "This campaign may be financially motivated, since the BeaverTail malware has the capability of stealing 13 different cryptocurrency wallets."