North Korea's Lazarus hacking group has once again exploited a zero-day vulnerability in Microsoft Windows to deploy malware on targeted devices. On August 13, Microsoft addressed this issue with its monthly Patch Tuesday updates, fixing a flaw in the Windows Ancillary Function Driver (Afd.sys) for WinSock, identified as CVE-2024-38193. Security experts strongly recommend applying this update promptly, as Microsoft has confirmed that the vulnerability is actively being exploited.

The flaw allows attackers to escalate system privileges through a use-after-free memory management issue, potentially granting them elevated system access, according to Rapid7. The advisory underscores the urgency of this patch, highlighting the low complexity of attacks, lack of required user interaction, and minimal privileges needed for exploitation.

The warning proved accurate, as Avast researchers Luigino Camastra and Martin Milanek, who initially discovered and reported the flaw to Microsoft in June, revealed that Lazarus had been exploiting this vulnerability before the fix was issued. Their primary aim was to install a rootkit named Fudmodule on the affected systems, utilizing the zero-day vulnerability to remain undetected by security software.

Details on the specific organizations targeted and their industries have not been disclosed. However, Lazarus is known for its focus on stealing cryptocurrency to support North Korea’s financially strained regime. The regime also uses its hacking teams to gather intelligence on Western nuclear facilities and defense systems.

This incident is part of a broader pattern of North Korean hacking activities targeting Windows drivers. In February, Microsoft patched another vulnerability, CVE-2024-21338, which Lazarus had used to gain system-level access. This flaw was in the appid.sys AppLocker driver, crucial for controlling application execution on Windows systems. Avast had previously reported this vulnerability, which was actively being exploited by Lazarus to install Fudmodule. The updated version of Fudmodule included enhancements, such as disabling antivirus protections like Microsoft Defender and CrowdStrike Falcon.

The rise of "Bring Your Own Vulnerable Driver" (BYOVD) attacks, where attackers use legitimate but vulnerable drivers to bypass security measures, has been noted. Lazarus has employed this tactic since at least October 2021, using it to infiltrate systems by loading drivers with known vulnerabilities. Other groups have also utilized similar methods, such as Sophos reporting on RansomHub's use of outdated drivers to disable endpoint detection and response tools, and deploying ransomware.

Overall, as Lazarus and similar groups continue to adapt their strategies, the need for vigilance and timely updates is crucial to protect systems from these sophisticated attacks.