Microsoft-Signed Kernel Driver Abused to Disable Security Tools and Harvest Credentials

Attackers are exploiting a vulnerability in a Microsoft-signed kernel driver, example_driver.sys, which facilitates arbitrary kernel memory read/write operations through IOCTL 0x80002000. By leveraging this trusted signature, threat actors bypass endpoint protection by unhooking security callbacks and subverting PatchGuard. This "Bring Your Own Vulnerable Driver" (BYOVD) technique enables unauthorized privilege escalation and the theft of sensitive credentials from LSASS, SAM, and domain controllers via DCsync. This method presents a critical risk by subverting the root of trust in the Windows kernel to evade detection and facilitate widespread lateral movement across high-value environments.

• Vulnerability and Technical Exploitation

  • Exploited Driver: example_driver.sys, signed by Microsoft Corporation (SHA256: a3f5c2e9b1d4f6a7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1).
  • Technical Flaw: Unrestricted kernel memory access provided via IOCTL 0x80002000.
  • Impact: Enables kernel-mode manipulation to disable security product hooks and bypass system protections.

• Attacker Workflow and Post-Exploitation

  • Initial Access: Delivery through phishing campaigns or malicious installers like setup.exe (SHA256: b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d).
  • Escalation: Loading the signed driver to patch or terminate EDR/AV security callbacks in kernel space.
  • Credential Theft: Utilizing user-mode tools to dump LSASS/SAM and executing DCsync attacks to compromise domain controllers.

• Detection and Monitoring Indicators

  • YARA Signature: Identifies the specific IOCTL pattern { 00 00 00 80 00 02 00 00 } used in the exploit.
  • Sigma/Sysmon: Monitors driver_load events specifically for Image: *\\example_driver.sys.
  • Telemetry: Watch for unusual IOCTL calls and driver loading from non-standard system directories.

• Mitigation and Defensive Guidance

  • System Hardening: Enforce strict driver signing policies and enable Hypervisor-Protected Code Integrity (HVCI) and Virtualization-Based Security (VBS).
  • Attack Surface Reduction: Implement ASR rules to block driver loads from untrusted sources (observed 70% prevention rate).
  • Behavioral Monitoring: Alert on the execution of suspicious installers and unauthorized modifications to kernel-mode callbacks.

• Observed Impact and Trends

  • Sector Targeting: 12 confirmed incidents spanning Finance, Healthcare, Government, and Technology.
  • Threat Metrics: Average dwell time of 42 days with approximately 3,500 credential sets compromised.
  • Control Efficacy: Driver signing enforcement yields a ~95% block rate, while HVCI provides an ~88% reduction in successful exploitation.