North Korean threat actors associated with the Contagious Interview campaign have adopted new tactics by leveraging JSON storage services such as JSON Keeper, JSONsilo, and npoint.io to host and deliver malware. These actors approach software developers, particularly those in cryptocurrency and Web3 sectors, via professional networking platforms like LinkedIn, posing as recruiters or collaborators. Victims are lured into downloading trojanized code projects from platforms like GitHub or GitLab, which contain hidden links to malicious payloads stored in JSON services. The initial payload, often disguised as an API key, leads to the download of JavaScript malware such as BeaverTail, which can harvest sensitive data and deploy additional backdoors like InvisibleFerret.
The campaign's modular approach allows for further payloads, including TsunamiKit, to be fetched from external sources like Pastebin or .onion addresses. The malware toolkit is capable of system fingerprinting, data collection, and persistent access, with some payloads specifically targeting multiple operating systems including Windows, Linux, and macOS. The Contagious Interview campaign remains focused on financial gain for the DPRK regime and demonstrates ongoing evolution in its social engineering and malware delivery techniques, as highlighted by recent research from NVISO and corroborated by other security firms.

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NVISO said it contacted the legitimate JSON storage providers whose services were being abused, and the providers were reportedly working to remove the malicious content.
NVISO disclosed technical analysis showing the JSON-hosted payload chain leading to a BeaverTail infostealer variant, followed by the InvisibleFerret Python RAT, with an added Tsunami-related component and Pastebin-based stage retrieval. The report also noted broader infrastructure pivots including Railway-hosted payload delivery and published IOCs.
In a newly observed evolution of the campaign, the threat actors began hiding malware delivery behind legitimate JSON storage services such as JSON Keeper, JSONsilo, and npoint.io, embedding base64-encoded URLs in trojanized demo project files.
By July 2025, researchers reported that the Lazarus-linked Contagious Interview campaign was using three distinct malware delivery methods to deploy BeaverTail, InvisibleFerret, and OtterCookie. The techniques included eval-based execution after POST requests, fragmented URLs with Vercel-hosted infrastructure, and try/catch abuse that simulated 500 API errors to evade static detection.
North Korea-linked Contagious Interview activity was active by November 2023, using fake recruiter-themed social engineering and trojanized coding tasks to target software developers, especially in cryptocurrency and Web3 roles.
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