Threat actors use stolen NVIDIA code signing certificates to sign malware to appear trustworthy and allow malicious drivers to be loaded into Windows.
This week, NVIDIA confirmed they were victims of a cyberattack that allowed threat actors to steal employee credentials and proprietary data.
The extortion group, known as Lapsus$, claims they stole 1TB of data during the attack and started leaking the data online after NVIDIA refused to negotiate with them.
Lapsus$ Messages About the NVIDIA Attack
The leak involves two stolen code signing certificates used by NVIDIA developers to sign their drivers and executables.
As part of #NvidiaLeaks, two code signing certificates have been compromised. Although they have expired, Windows still allows them to be used for driver signing. See the lecture I gave on BH/DC for more context on leaked certificates: https://t.co/UWu3AzHc66 pic.twitter.com/gCrol0BxHd
— Bill Demirkapi (@BillDemirkapi) March 3, 2022
A code signing certificate allows developers to digitally sign executable files and drivers so Windows and end users can verify who owns the file and whether it has been tampered with by a third party.
To increase security in Windows, Microsoft also requires kernel-mode drivers to be code signed before the operating system loads them.
NVIDIA certificates used to sign malware
After Lapsus$ Leaked NVIDIA’s Code Signing Certificates, security researchers quickly found that the certificates were used to sign malware and other tools used by threat actors.
According to samples uploaded to the VirusTotal malware scanning service, the stolen certificates were used to sign various malware and hacking tools, such as Cobalt Strike beacons, Mimikatz, backdoors, and remote access trojans.
For example, a threat actor used the certificate to sign a Quasar remote access trojan [VirusTotal]while someone else used the certificate to sign a Windows driver [VirusTotal]†
Quasar RAT Signed by NVIDIA Certificate
Security Researchers Kevin Beaumont and Will Dormann shared that the stolen certificates use the following serial numbers:
43BB437D609866286DD839E1D00309F5 14781bc862e8dc503a559346f5dcc518
Some files were probably uploaded to VirusTotal by security researchers, but others appear to be used by threat actors for malware campaigns [1, 2]†
Even though both stolen NVIDIA certificates have expired, Windows still allows a driver signed with the certificates to be loaded into the operating system.
By using these stolen certificates, threat actors gain the advantage that their programs look like legitimate NVIDIA programs and that malicious drivers can be loaded by Windows.
Signed Quasar RAT Sample
To prevent known vulnerable drivers from loading into Windows, David Weston, director of Enterprise and OS Security at Microsoft, tweeted that administrators can configure Windows Defender Application Control policies to determine which NVIDIA drivers can be loaded.
WDAC policies work on both 10-11 with no hardware requirements up to the home SKU, despite some FUD misinformation I’ve seen, so it should be your first choice. Create a policy with the wizard, then add a deny rule or allow specific versions of Nvidia if needed
— David Weston (DWIZZZLE) (@dwizzzleMSFT) March 3, 2022
However, using WDAC is not an easy task, especially for non-IT Windows users.
Due to the potential for abuse, it is hoped that the stolen certificates will be added to Microsoft’s certificate revocation list in the future to prevent malicious drivers from being loaded into Windows.
However, doing so will also block legitimate NVIDIA drivers, so we probably won’t see this happen anytime soon.
This post Malware now uses stolen NVIDIA certificates for code signing
was original published at “https://www.bleepingcomputer.com/news/security/malware-now-using-stolen-nvidia-code-signing-certificates/”
