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Ransomware Operator Abuses Anti-Cheat Driver to Disable Antiviruses

A vulnerable anti-cheat driver for the Genshin Impact video game has been abused by a threat actor to disable antivirus programs to facilitate the deployment of ransomware, cybersecurity firm Trend Micro reports.

A vulnerable anti-cheat driver for the Genshin Impact video game has been abused by a threat actor to disable antivirus programs to facilitate the deployment of ransomware, cybersecurity firm Trend Micro reports.

The driver, mhyprot2.sys, provides anti-cheat functions, but can be used to bypass privileges from user mode to kernel mode and to kill the processes and services associated with endpoint protection applications.

The use of the driver, Trend Micro notes, is independent of the Genshin Impact game, and remains on user devices even after the game has been uninstalled.

According to the cybersecurity firm, the driver is signed with a valid certificate, meaning that it continues to work on users’ computers, thus exposing them to malicious abuse. What’s more, Trend Micro believes that other malware families might soon start targeting it as well.

“This ransomware was simply the first instance of malicious activity we noted. The threat actor aimed to deploy ransomware within the victim’s device and then spread the infection. Since mhyprot2.sys can be integrated into any malware, we are continuing investigations to determine the scope of the driver,” the company’s security researchers say.

The mhyprot2.sys module is easy to obtain and proof-of-concept (PoC) code exploiting it to read/write kernel memory, terminate processes, and enumerate system resources has been available publicly since October 2020, shortly after Genshin Impact was released.

The driver’s versatility, coupled with the existence of well-made PoC code suggests that the driver is likely used more prevalently than some known rootkits, the researchers say.

As part of an analyzed attack, the threat actor was seen deploying to the domain controller a malicious Windows installer posing as AVG Internet Security, which dropped and executed, among other files, the vulnerable driver. According to Trend Micro, the adversary was likely attempting to mass-deploy the ransomware from the domain controller, via a startup/logon script.

“It is still rare to find a module with code signing as a device driver that can be abused. The point of this case is that a legitimate device driver module with valid code signing has the capability to bypass privileges from user mode to kernel mode,” the cybersecurity firm notes.

miHoYo, the developer of Genshin Impact, has been informed of the vulnerable driver and the potential abuse, but the driver is still valid at this time. For as long as its signing certificate remains valid, the driver may be abused for malicious purposes.

“This module is very easy to obtain and will be available to everyone until it is erased from existence. It could remain for a long time as a useful utility for bypassing privileges. Certificate revocation and antivirus detection might help to discourage the abuse, but there are no solutions at this time because it is a legitimate module,” Trend Micro says.

Related: Chinese UEFI Rootkit Found on Gigabyte and Asus Motherboards

Related: New Black Basta Ransomware Possibly Linked to Conti Group

Related: ALPHV Ransomware Operators Pressure Victim With Dedicated Leak Site

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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