North Korean Hackers Deploy New OtterCookie Malware Targeting Software Developers

North Korean threat actors are deploying a new JavaScript malware called OtterCookie as part of the ongoing Contagious Interview campaign, targeting software developers through sophisticated social engineering techniques.

The Contagious Interview campaign, first detailed by Palo Alto Networks in November 2023, has been active since at least December 2022. Unlike typical nation-state cyber espionage operations, this campaign appears to be financially motivated and targets a broad range of organizations.

Researchers from NTT Security have observed the emergence of OtterCookie, a new malware variant that has been active since September 2024, with a notable variant appearing in November. The malware is distinct from previous threats like BeaverTail and InvisibleFerret that were associated with the campaign.

The attack chain typically begins with malicious Node.js projects or npm packages downloaded from platforms like GitHub and Bitbucket. Recently, attackers have expanded their approach to include applications built with Qt and Electron frameworks, demonstrating their evolving tactics to exploit software development ecosystems.

OtterCookie's infection mechanism involves sophisticated loaders that retrieve JSON data and execute the 'cookie' property as JavaScript code. In some cases, the malware can be deployed alongside BeaverTail or independently, showing the attackers' flexibility in their approach.

The November version of OtterCookie utilizes Socket.IO for remote communication, enabling threat actors to execute shell commands and steal device information. Researchers observed the malware collecting cryptocurrency wallet keys from various file types, including documents, images, and cryptocurrency-related files.

A significant evolution in the November variant is its ability to exfiltrate clipboard data, which can potentially capture sensitive information like login credentials or private messages. This improvement builds upon the September version's capabilities, which primarily used regular expressions to detect cryptocurrency-related keys.

The malware's reconnaissance capabilities are notable, with attackers using commands like 'ls' and 'cat' to explore the target environment and prepare for potential lateral movement. This suggests a methodical approach to compromising systems and gathering intelligence.

Security experts emphasize that the Contagious Interview campaign continues to experiment and update its attack methods. The group's activities have been observed in multiple regions, including Japan, highlighting the widespread nature of these threats.

Software developers are advised to exercise extreme caution when receiving job offers or code-related communications, particularly those involving unfamiliar sources or requiring unusual code execution as part of potential job tests.

The emergence of OtterCookie underscores the ongoing sophistication of North Korean threat actors in targeting the software development community through increasingly complex and adaptive malware strategies.

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