North Korean Hackers Deploy DocSwap Malware Disguised as Security Tool

In a recent cybersecurity threat discovery, the S2W Threat Research and Intelligence Center Talon has identified and analyzed a new type of malware linked to a North Korean-backed Advanced Persistent Threat (APT) group.

The malware, masquerading as a “문서열람 인증 앱” (Document Viewing Authentication App), was first detected on December 13, 2024.

This sophisticated threat has been designated as DocSwap due to its connection with a phishing page impersonating CoinSwap found at its command and control (C2) infrastructure.

Overview of DocSwap Malware

• Masquerade as Security Tool: The malware disguises itself as a document-viewing authentication app, targeting mobile device users, particularly in South Korea.
• Decryption and Execution: It decrypts an internal “security.db” file using an XOR operation and dynamically loads a DEX file, which leads to malicious activities like keylogging and information theft.
• Phishing Connection: Initially linked to a CoinSwap phishing page, later displaying Naver’s favicon and a peculiar message, hinting at a possible connection with the Kimsuky group.

Detailed Analysis

When executed, the malware prompts users to grant various permissions, including those for keylogging via accessibility services.

It maintains persistence by generating notifications to request these permissions and by using the StartForeground API to keep itself active even after a system restart.

The threat actors behind this malware have been identified as part of the puNK group, specifically puNK-004, as per a report by Security Researcher in Medium.

This group is tracked by S2W TALON, which monitors various entities linked to North Korea under the puNK classification.

The deployment of DocSwap highlights the evolving tactics of North Korean hackers, who are increasingly leveraging sophisticated phishing and malware techniques to target specific regions, like South Korea.

This threat underscores the importance of vigilance among mobile users, particularly when downloading and granting permissions to apps.

Recommendations

• Be cautious with app installations, especially when apps request extensive permissions.
• Use robust antivirus software that can detect and block such threats.
• Regularly update devices to ensure the latest security patches are applied.

As cybersecurity threats continue to evolve, users and organizations must stay informed and take proactive measures to protect themselves against these sophisticated attacks.

The emergence of DocSwap malware serves as a reminder of the constant threat landscape faced by mobile device users.

By staying alert and employing best practices in cybersecurity, we can mitigate these risks. The collaboration between cybersecurity researchers and the broader community is essential in combating these threats and ensuring a safer digital environment.

As technology advances, so do the methods of cyber attackers. The awareness and proactive measures taken by users play a crucial role in safeguarding against these threats.

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