North Korean hackers installed rootkits on thousands of PCs via Windows zero-day vulnerability

Cybersecurity researchers have discovered that the hacker group Lazarus, believed to be linked to the North Korean government, used a zero-day vulnerability in Windows to install a sophisticated FudModule rootkit. The vulnerability allows you to gain maximum rights in the system.

Image source: anonymous_Pete-Linforth/Pixabay

As reported by Ars Technica with reference to representatives of the Gen company, the vulnerability, which received the identifier CVE-2024-38193, belongs to the “use after free” class and is located in the AFD.sys driver, which is used to work with the Winsock protocol and serves as an entry point into operating system kernel. Microsoft has warned that this vulnerability could be used by attackers to gain system privileges that allow them to execute unverified code.

«The vulnerability allowed attackers to bypass standard security mechanisms and gain access to sensitive areas of the system that are inaccessible to most users and even administrators, says the Gen report. “This type of attack is complex and resource-intensive, and its cost on the black market can reach several hundred thousand dollars.” Recall that the FudModule rootkit was first discovered in 2022. It is able to hide its malicious presence in the system, bypassing antiviruses and other security measures.

Previously, Lazarus hackers used the “Bring your own vulnerable driver” technique to install earlier versions of FudModule. However, this time they took advantage of a bug in the appid.sys system driver, which was present by default in all versions of Windows until today.

Gen has not disclosed details regarding how long hackers have been exploiting the CVE-2024-38193 vulnerability, how many organizations have been affected by the attacks, or whether antivirus programs were able to detect the latest version of FudModule.