The North Korean-backed hacking group Kimsuky has shifted its focus towards exploiting Remote Desktop Protocol (RDP) for remote access to compromised systems. According to AhnLab Security Intelligence Center (ASEC), Kimsuky developed a custom version of the open-source RDP Wrapper to enable remote desktop functionality on systems that do not natively support RDP. This modified tool allows Kimsuky to bypass antivirus detections and gain persistent access to infected devices, making it a key component of the group’s evolving cyber attack methods.
Kimsuky’s attack strategy begins with spear-phishing emails that contain malicious shortcut files designed to look like legitimate documents, such as PDFs or Excel spreadsheets. Once opened, these files execute PowerShell or Mshta commands to download additional malicious payloads. Two major tools used in the attack are PebbleDash, a backdoor, and the custom RDP Wrapper. This wrapper enables the attackers to activate remote desktop services on systems without native support, allowing them to control the infected machines remotely and undetected.
To circumvent network restrictions and gain access to systems behind firewalls or in private networks, Kimsuky employs proxy malware. This malware facilitates smooth RDP connections between the infected systems and external networks. Additionally, the group uses keyloggers, which are deployed via PowerShell scripts or executable files, to record user keystrokes and steal sensitive data such as credentials stored in web browsers. These tools help Kimsuky collect valuable information that can be exploited in further attacks.
As Kimsuky adapts and becomes more sophisticated, cybersecurity experts emphasize the importance of proactive defense measures. Recommendations include avoiding email attachments from unknown sources, ensuring systems are regularly updated to patch vulnerabilities, using strong passwords, and enabling multi-factor authentication (MFA). The increase in Kimsuky’s use of RDP highlights the growing complexity of state-sponsored cyber threats, underlining the need for organizations to remain vigilant and implement comprehensive security measures to protect against such persistent attacks.
