The “Contagious Interview” campaign, attributed to North Korean threat actors, has intensified with the release of 67 additional malicious packages on the npm registry. These packages, which have already garnered over 17,000 downloads, introduce a novel malware loader dubbed XORIndex, signifying an expansion of a previous attack wave from last month that involved 35 npm packages distributing the HexEval loader. This activity underscores a continuous “whack-a-mole” dynamic where defenders identify and report malicious code, prompting the attackers to quickly deploy new, similar variants.
“Contagious Interview,” also known by several other names including DeceptiveDevelopment and Void Dokkaebi, is a long-standing operation designed to trick developers into downloading and executing a seemingly legitimate open-source project. This tactic is believed to complement Pyongyang’s broader remote IT worker scheme by targeting developers already employed within companies of interest, rather than directly seeking employment. The primary goal of these attacks is to establish a foothold for further malicious activities.
The attack chain initiated by these malicious npm packages is straightforward, acting as a delivery mechanism for a known JavaScript loader and stealer called BeaverTail.
This initial compromise allows for the exfiltration of sensitive data from web browsers and cryptocurrency wallets. Subsequently, the BeaverTail malware is used to deploy a Python backdoor, referred to as InvisibleFerret, establishing persistent access to compromised systems.
Both the newly introduced XORIndex loader and the previously observed HexEval loader operate similarly, profiling the compromised machine and communicating with hard-coded command-and-control (C2) infrastructure to obtain the host’s external IP address. This collected information is then transmitted to a remote server before BeaverTail is launched. Analysis reveals that the XORIndex loader has undergone a steady evolution, progressing from a basic prototype to a more sophisticated and stealthier form, incorporating features like rudimentary system reconnaissance in its later iterations.
Experts anticipate that the “Contagious Interview” threat actors will continue to diversify their malware arsenal, consistently rotating through new npm maintainer aliases and reusing existing malware families like BeaverTail and InvisibleFerret, while actively deploying new variants such as the XORIndex loader. This ongoing threat emphasizes the critical need for vigilance within the open-source software supply chain. Adding to the concern, Russian-linked cybercriminals have also been observed manipulating npm download metrics to falsely legitimize their malicious packages, highlighting a broader trend of supply chain attacks.
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