From primitive crypto theft to sophisticated AI-based deception

This blogpost introduces our latest white paper, presented at Virus Bulletin 2025, where we detail the operations of the North Korea-aligned threat actor we call DeceptiveDevelopment and its connections to North Korean IT worker campaigns. The white paper provides full technical details, including malware analysis, infrastructure, and OSINT findings. Here, we summarize the key insights and highlight the broader implications of this hybrid threat.

Key points of this blogpost:

• The invention and focus of the operations are on the social-engineering methods.
• DeceptiveDevelopment’s toolset is mostly multiplatform and consists of initial obfuscated malicious scripts in Python and JavaScript, basic backdoors in Python and Go, and a dark web project in .NET.
• We provide insights into operational details of North Korean IT workers, like work assignments, schedules, communication with clients, etc., gathered from public sources.
• Native, more complex Windows backdoors are an occasional addition in the execution chain and are likely shared by other North Korea-aligned actors.
• DeceptiveDevelopment and North Korean IT workers have different objectives and means, but we consider them as tightly connected.

Introduction

In this blogpost, we examine the DeceptiveDevelopment group and the WageMole activity cluster as two tightly connected North Korea-aligned entities. WageMole is a label that we have adopted for activities associated with North Korean IT workers. While the campaigns of both are driven by financial gain, each plays a distinct and complementary role in relation to the other:

• DeceptiveDevelopment operators pose as recruiters, using fraudulent job offers to compromise the systems of job seekers.
• North Korean IT workers then use the information gained by the DeceptiveDevelopment operators to pose as job seekers. To secure a real job position, they may employ several tactics, including proxy interviewing, using stolen identities, and fabricating synthetic identities with AI-driven tools.

First, we provide a catalogue of multiplatform tools used by DeceptiveDevelopment, from simple but obfuscated scripts like BeaverTail and InvisibleFerret to a complex toolkit, TsunamiKit, centered around a .NET backdoor. We also disclose specific links between more complex backdoors used by DeceptiveDevelopment, AkdoorTea and Tropidoor, and other, more APT-oriented North Korea-aligned operations. Next, we describe interesting aspects of North Korean IT workers’ modus operandi, obtained from public sources, mostly from unintentionally exposed data, testimonials of victims, and investigations of independent researchers..

DeceptiveDevelopment 

DeceptiveDevelopment is a North Korea-aligned group active since at least 2023, focused on financial gain. Its activities overlap with Contagious Interview, DEV#POPPER, and Void Dokkaebi. The group targets software developers on all major systems – Windows, Linux, and macOS – and especially those in cryptocurrency and Web3 projects. Initial access is achieved exclusively via various social engineering techniques like ClickFix, and fake recruiter profiles similar to Lazarus’s Operation DreamJob, to deliver trojanized codebases during staged job interviews. Its most typical payloads are the BeaverTail, OtterCookie, and WeaselStore infostealers, and the InvisibleFerret modular RAT.

Targeting strategy

DeceptiveDevelopment operators use various methods to compromise their victims, relying on clever social engineering tricks. Via both fake and hijacked profiles, they pose as recruiters on platforms like LinkedIn, Upwork, Freelancer, and Crypto Jobs List. They offer fake lucrative job opportunities to attract their targets’ interest. Victims are requested to participate in a coding challenge or a pre-interview task. The task involves downloading a project from private GitHub, GitLab, or Bitbucket repositories. These repositories contain trojanized code, often hidden cleverly in long comments displayed well beyond the right-hand edge of a code browser or editor window. Participation in the task triggers the execution of BeaverTail, the first-stage malware.

Besides these fake recruiter accounts, the addition of a new social engineering technique known as ClickFix was observed. ClickFix in relation to DeceptiveDevelopment was first reported by Sekoia.io in March 2025, when it was used by the group as the initial access method on macOS and Windows systems; in September 2025, GitLab spotted it being used on Linux systems too. The attackers direct the victim to a fake job interview website, containing an application form that they are asked to complete. The application form contains a few lengthy questions related to the applicant’s identity and qualifications, leading the victim to put significant time and effort into filling in the form and making them feel like they are almost done, and therefore more likely to fall for the trap. In the final step of the application, the victim is asked to record a video of them answering the final question. The site triggers a pop-up asking the victim to allow camera access, but the camera is never actually accessed. Instead, an error message appears saying that access to the camera or microphone is currently blocked and offers a “How to fix” link. That link leads to a pop-up employing the ClickFix social engineering technique. The victim is instructed, based on their operating system, to open a terminal and copy and paste a command that should solve the issue. However, instead of enabling the victim’s camera, the command downloads and executes malware.

Toolset

BeaverTail and InvisibleFerret

The first indication of DeceptiveDevelopment activity came in November 2023, when Unit 42 reported the Contagious Interview campaign; we later associated this campaign with the group. Unit 42 coined the names BeaverTail and InvisibleFerret for the two malware families used in this campaign. We documented this campaign in more detail in our WeLiveSecurity blogpost from February 2025, dissecting how the threat actor makes use of these two malware families.

BeaverTail is a simple infostealer and downloader that collects data from cryptocurrency wallets, keychains, and saved browser logins. We have observed variants of this malware written in JavaScript, hidden in fake job challenges, and also in C++, using the Qt framework and disguised as conferencing software. Its primary function is downloading the second-stage malware InvisibleFerret. At the end of 2024, a new malware family with functionality similar to BeaverTail emerged – it was named OtterCookie by NTT Security. OtterCookie is written in JavaScript and uses very similar obfuscation techniques. We believe that OtterCookie is an evolution of BeaverTail and is used by some teams within DeceptiveDevelopment instead of the older BeaverTail, while other teams continue using and modifying the original codebase.

InvisibleFerret is modular malware written in Python with more information-stealing capabilities than BeaverTail, also capable of providing remote control to attackers. It usually comes with the following four modules:

• a browser-data stealer module (extracts and exfiltrates data saved by browsers and cryptocurrency wallets),
• a payload module (remote access trojan),
• a clipboard module (containing keylogging and clipboard logging capabilities) – in some cases distributed as part of the payload module, and
• an AnyDesk module (which deploys the AnyDesk remote access tool to allow direct attacker access to the compromised machine).

WeaselStore

As DeceptiveDevelopment evolved and started to include more teams in its operations, those teams started modifying the codebase to meet their own needs and introduced new malware tooling. One such example is a campaign that ESET researchers investigated in August 2024. In addition to the conventional BeaverTail and InvisibleFerret malware, the team responsible for the campaign deployed what we believe is its own new malware – which we named WeaselStore.

WeaselStore (also called GolangGhost and FlexibleFerret) is a multiplatform infostealer written in Go, though in May 2025, Cisco Talos reported about WeaselStore being rewritten in Python; they called that malware PylangGhost. As the implementation is identical, for simplicity, we refer to both implementations as WeaselStore in this blogpost.

WeaselStore’s functionality is quite similar to both BeaverTail and InvisibleFerret, with the main focus being exfiltration of sensitive data from browsers and cryptocurrency wallets. Once the data has been exfiltrated, WeaselStore, unlike traditional infostealers, continues to communicate with its C&C server, serving as a RAT capable of executing various commands.

The most interesting aspect of WeaselStore in Go is that it is delivered to the victim’s system in the form of Go source code, along with the Go environment binaries necessary to build and execute it, allowing the malware to target three main operating systems – Windows, Linux, and macOS (see Figure 1). The installation mechanism differs based on the victim’s operating system, but in all cases the chain ends with downloading the WeaselStore Go source code and then compiling and executing it using a Go build environment, which is also provided alongside.

TsunamiKit

In November 2024, a new version of the InvisibleFerret malware delivered a modified browser-data stealer module. This module, in addition to its normal functionality, contains a previously unseen, large, encoded block with the first stage of the execution chain deploying a completely new malware toolkit, also intended for information and cryptocurrency theft. We named this toolkit TsunamiKit, based on the developer’s repeated use of “Tsunami” in the names of its components (see Table 1). The threat being publicly reported by Alessio Di Santo in November 2024 and by Bitdefender in February 2025; our white paper adds context by placing it in the overall DeceptiveDevelopment modus operandi. The paper also dives into the details of TsunamiKit’s complex execution chain.

Table 1. Components of the TsunamiKit execution chain

* These components were originally both named TsunamiPayload; we have renamed them to avoid any confusion.

PostNapTea and Tropidoor

Over the course of our research, we spotted an interesting piece of evidence, further linking DeceptiveDevelopment to North Korea. In April 2025, Ahnlab researchers reported about trojanized Bitbucket projects containing BeaverTail and a 64‑bit downloader named car.dll or img_layer_generate.dll. While BeaverTail, as expected, downloaded InvisibleFerret, this new downloader retrieved an in-memory payload that was named Tropidoor by Ahnlab. We realized that Tropidoor shares large portions of code with PostNapTea, a Lazarus RAT distributed via exploitation against South Korean targets in 2022. Table 2 contains a comparison of both payloads.

Table 2. Comparison of Tropidoor (DeceptiveDevelopment) and PostNapTea (Lazarus) payloads (asterisks indicate the country of a VirusTotal submission)

Tropidoor is the most sophisticated payload yet linked to the DeceptiveDevelopment group, probably because it is based on malware developed by the more technically advanced threat actors under the Lazarus umbrella. Some of the supported commands are shown in Figure 2.

New findings

Since our white paper’s submission, we have uncovered new findings that further strengthen the link between the activity of DeceptiveDevelopment and other North Korea-aligned cyberattacks.

We discovered that the TsunamiKit project dates back at least to December 2021, when it was submitted to VirusTotal under the name Nitro Labs.zip. One of the components contains the PDB path E:\Programming\The Tsunami Project\Malware\C#\C# Tsunami Dist Version 3.0.0\CTsunami\obj\Release\netcoreapp3.1\win-x64\\System Runtime Monitor.pdb. We conclude that TsunamiKit is likely a modification of a dark web project rather than a new creation by the attackers, based on TsunamiKit largely predating the approximate start of DeceptiveDevelopment activity in 2023, similar TsunamiKit payloads without any signs of BeaverTail having been observed in ESET telemetry, and cryptocurrency mining being a core feature of TsunamiKit.

AkdoorTea

In August 2025, a BAT file named ClickFix-1.bat and a ZIP archive named nvidiaRelease.zip were uploaded to VirusTotal. The BAT file just downloads the archive and executes run.vbs from it. The archive contains various legitimate JAR packages for the NVIDIA CUDA Toolkit, together with the following malicious files:

• shell.bat, a trojanized installer for Node.js, which is executed afterward.
• main.js, an obfuscated BeaverTail script, automatically loaded by Node.js.
• drvUpdate.exe, a TCP RAT, to which we assign the codename AkdoorTea, as it is similar to Akdoor reported by AlienVault in 2018 (see Table 3). Akdoor is a detection root name by Ahnlab and usually identifies a North Korea-aligned payload.
• run.vbs, a VBScript that executes the trojanized installer and AkdoorTea.

Table 3. Comparison of variants of AkdoorTea and Akdoor

One of the differences between AkdoorTea from 2025 and Akdoor from 2018 is the numbering of commands; see Figure 3. Also, the command name “version” is called “shi” now.

North Korean IT workers (aka WageMole)

While our research into DeceptiveDevelopment is primarily based on data from our telemetry and reverse-engineering the group’s toolset, it is interesting to point out DeceptiveDevelopment’s relations to fraud operations by North Korean IT workers, overlapping with the activity of the UNC5267 and Jasper Sleet threat groups.

IT worker campaigns have been ongoing since at least April 2017, according to an FBI wanted poster, and have been increasingly prominent in recent years. A joint advisory released in May 2022 describes IT worker campaigns as a coordinated effort by North Korea-aligned individuals to gain employment at overseas companies, whose salaries are then used to help fund the country. They have also been known to steal internal company data and use it to extort companies, as stated in an announcement by the FBI in January 2025.

In addition to using AI to perform their job tasks, they rely heavily on AI for manipulating photos in their profile pictures and CVs, and even perform face swaps in real-time video interviews to look like the persona they are currently using, as described in more detail in a blogpost by Unit 42 in April 2025.

A methodological insight was provided by a DTEX report in May 2025. The IT workers reportedly operate in a scattered manner, with numerous teams of workers, usually based in foreign countries like China, Russia, and countries in Southeast Asia. Each team works in a slightly different manner, but their end goals and modus operandi are the same – posing as foreign remote workers with fake documents and CVs, and looking for remote employment or freelance work to gather funds from the salaries.

Analyzing OSINT data

Multiple researchers have observed ties and instances of information exchange between these IT workers and DeceptiveDevelopment. In August 2024, the cybersecurity researcher Heiner García published an investigation of how both groups share email accounts or are mutually followed between the GitHub profiles of fake recruiters and IT workers. In November 2024, Zscaler confirmed that identities stolen from compromised victims are used by scammers to secure remote jobs. This leads us to assert with medium confidence that although these activities are conducted by two different groups, they are most likely connected and collaborating.

Additionally, we managed to gather publicly available data detailing the inner workings of some of the IT worker teams. We gathered this information from multiple sources (with significant help from @browsercookies on X), among them GitHub profiles belonging to the IT workers, containing publicly accessible internal data and content shared publicly by researchers. These include details of their work assignments, schedules, communication with clients and each other, emails, various pictures used for online profiles (both real and fake), fake CVs, and text templates used when job hunting; due to information sharing agreements, we are not disclosing the specific sources of the data used in our analysis. We dive into these details in our white paper, and provide a compact summary below.

Analysis of fake CVs and internal materials shows that IT workers initially targeted jobs in the US, but have recently shifted focus to Europe, including France, Poland, Ukraine, and Albania.

Each team is led by a “boss” who sets quotas and coordinates work. Members spend 10–16 hours daily acquiring jobs, completing tasks, and self-educating – mainly in web programming, blockchain, English, and AI integration.

They meticulously track their work and use fake identities, CVs, and portfolios to apply for jobs. Communication with employers follows scripted responses to appear qualified.

Additionally, they use premade scripts to recruit real people as proxies, offering them a share of the salary to attend interviews or host work devices in less suspicious countries. In one case, Ukrainian developers were targeted due to perceived hiring advantages.

Conclusion

DeceptiveDevelopment’s TTPs illustrate a more distributed, volume-driven model of its operations. Despite often lacking technical sophistication, the group compensates through scale and creative social engineering. Its campaigns demonstrate a pragmatic approach, exploiting open-source tooling, reusing available dark web projects, adapting malware probably rented from other North Korea-aligned groups, and leveraging human vulnerabilities through fake job offers and interview platforms.

The activities of North Korean IT workers constitute a hybrid threat. This fraud-for-hire scheme combines classical criminal operations, such as identity theft and synthetic identity fraud, with digital tools, which classify it as both a traditional crime and a cybercrime (or eCrime). Proxy interviewing poses a severe risk to employers, since an illegitimate employee hired from a sanctioned country may not only be irresponsible or underperforming, but could also evolve into a dangerous insider threat.

Our findings also highlight the blurred lines between targeted APT activity and cybercrime, particularly in the overlap between malware campaigns by DeceptiveDevelopment and the operations of North Korean IT workers. These dual-use tactics – combining cybertheft and cyberespionage with non-cyberspace employment-fraud schemes – underscore the need for defenders to consider broader threat ecosystems rather than isolated campaigns..

For any inquiries about our research published on WeLiveSecurity, please contact us at threatintel@eset.com. 

ESET Research offers private APT intelligence reports and data feeds. For any inquiries about this service, visit the ESET Threat Intelligence page.

IoCs

Files

A comprehensive list of indicators of compromise (IoCs) and samples can be found in our GitHub repository.

Network

MITRE ATT&CK techniques

This table was built using version 17 of the MITRE ATT&CK framework.