North Korean APT Kimsuky Uses forceCopy Malware to Steal Browser-Stored Credentials

The North Korea-linked nation-state hacking group known as Kimsuky has been observed conducting spear-phishing attacks to deliver an information stealer malware named forceCopy, according to new findings from the AhnLab Security Intelligence Center (ASEC).

The attacks commence with phishing emails containing a Windows shortcut (LNK) file that’s disguised as a Microsoft Office or PDF document.

Opening this attachment triggers the execution of PowerShell or mshta.exe, a legitimate Microsoft binary designed to run HTML Application (HTA) files, that are responsible for downloading and running next-stage payloads from an external source.

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The South Korean cybersecurity company said the attacks culminated in the deployment of a known trojan dubbed PEBBLEDASH and a custom version of an open-source Remote Desktop utility named RDP Wrapper.

Also delivered as part of the attacks is a proxy malware that allows the threat actors to establish persistent communications with an external network via RDP.

Furthermore, Kimsuky has been observed using a PowerShell-based keylogger to record keystrokes and a new stealer malware codenamed forceCopy that’s used to copy files stored in web browser-related directories.

“All of the paths where the malware is installed are web browser installation paths,” ASEC said. “It is assumed that the threat actor is attempting to bypass restrictions in a specific environment and steal the configuration files of the web browsers where credentials are stored.”

The use of tools RDP Wrapper and proxies to commandeer infected hosts points to tactical shift for Kimsuky, which has historically leveraged bespoke backdoors for this purpose.

The threat actor, also referred to as APT43, Black Banshee, Emerald Sleet, Sparkling Pisces, Springtail, TA427, and Velvet Chollima, is assessed to be affiliated with the Reconnaissance General Bureau (RGB), North Korea’s primary foreign intelligence service.

Active since at least 2012, Kimusky has a track record of orchestrating tailored social engineering attacks that are capable of bypassing email security protections. In December 2024, cybersecurity company Genians revealed that the hacking crew has been sending phishing messages that originate from Russian services to conduct credential theft.

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