QILIN & WARLOCK RANSOMWARE: How BYOVD Attacks Silently Kill Your EDR Before Encryption – A Deep Dive + Video

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Introduction:

Bring Your Own Vulnerable Driver (BYOVD) attacks have become the weapon of choice for modern ransomware gangs like Qilin and Warlock. By exploiting legitimate but flawed kernel drivers, attackers disable over 300 EDR processes and kernel callbacks before deploying encryption, leaving traditional defenses blind. This article dissects the BYOVD technique, provides hands-on detection and mitigation steps, and arms you with commands to harden your Windows endpoints against these kernel‑level assaults.

Learning Objectives:

  • Understand how Qilin and Warlock use side‑loaded DLLs and vulnerable drivers to kill EDR/AV processes.
  • Learn to enumerate, block, and monitor vulnerable driver loads using native Windows tools and PowerShell.
  • Implement kernel‑level hardening measures including Windows Defender Application Control (WDAC) and Sysmon to detect BYOVD attempts.

You Should Know:

1. Enumerating Currently Loaded Kernel Drivers

Attackers first identify which vulnerable drivers are present. You can do the same to spot suspicious entries.

Step‑by‑step guide:

1. Open an elevated Command Prompt or PowerShell.

2. Run the built‑in driver query tool:

driverquery /v /fo csv > C:\driver_inventory.csv

3. For a more detailed list with digital signatures:

Get-WindowsDriver -Online | Select-Object Driver, ProviderName, Date, Version | Export-Csv C:\drivers_online.csv

4. Cross‑reference driver names against known vulnerable lists (e.g., from loldrivers.io). Look for unsigned or outdated drivers from well‑known abused vendors (e.g., ASIO, MSI, GigaByte).

Linux alternative: While BYOVD is Windows‑specific, on Linux monitor kernel modules with `lsmod` and verify signatures via `modinfo` and kernel module signing enforcement.

  1. Blocking Vulnerable Driver Loads with WDAC (Windows Defender Application Control)
    WDAC can prevent both known and unknown vulnerable drivers from loading, stopping BYOVD at the kernel gate.

Step‑by‑step guide:

1. Generate a baseline policy in audit mode:

$Policy = New-CIPolicy -Level Publisher -FilePath C:\WDAC\BasePolicy.xml -UserPEs

2. Add a deny rule for specific driver hashes or publishers. For example, to block a known vulnerable driver by SHA256:

Add-CIPolicyRule -FilePath C:\WDAC\BasePolicy.xml -DriverFilePath C:\BadDriver.sys -HashOnly

3. Convert to binary and deploy:

ConvertFrom-CIPolicy -XmlFilePath C:\WDAC\BasePolicy.xml -BinaryFilePath C:\WDAC\SiPolicy.p7b
Copy-Item C:\WDAC\SiPolicy.p7b C:\Windows\System32\CodeIntegrity\SiPolicy.p7b

4. Reboot and verify using Get-CIPolicy. Monitor event ID 3076 (blocked driver) in Event Viewer under Applications and Services Logs/Microsoft/Windows/CodeIntegrity/Operational.

3. Real‑time Detection Using Sysmon and Event Tracing

Qilin’s side‑loaded DLL and vulnerable driver installation leave forensic artifacts. Sysmon (System Monitor) captures them.

Step‑by‑step guide:

  1. Install Sysmon with a configuration targeting driver load events (Event ID 6): 
    sysmon64.exe -accepteula -i c:\tools\sysmon.xml

2. Example `sysmon.xml` snippet for driver load monitoring:

<EventFiltering>
<DriverLoad onmatch="include">
<Image condition="contains">.sys</Image>
</DriverLoad>
</EventFiltering>

3. Forward events to a SIEM or review locally with PowerShell:

Get-WinEvent -FilterHashtable @{LogName='Microsoft-Windows-Sysmon/Operational'; ID=6} | Where-Object {$_.Message -match "Signed.FALSE"}

4. Alert on any driver load with `Signed=FALSE` or with known vulnerable driver names (e.g., gdrv.sys, zamguard64.sys, mhyprot2.sys).

  1. Hardening the EDR Process Landscape Against Kill Commands
    Attackers often terminate EDR processes via `ZwTerminateProcess` called from kernel mode. You can protect critical processes.

Step‑by‑step guide:

  1. Enable Process Protection via Windows Defender Exploit Guard (Attack Surface Reduction rules): 
    Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A -AttackSurfaceReductionRules_Actions Enabled
  2. Use Group Policy to add EDR executables to the “Protected Process Light” (PPL) list:

– Navigate to Computer Configuration -> Administrative Templates -> System -> Process Mitigation Options.
– Add `C:\Program Files\YourEDR\EdrSvc.exe` with “Enable Process Protection” = “Light”.

3. Verify PPL status via Command

fltmc instances
tasklist /m /fi "imagename eq EdrSvc.exe"

4. For advanced protection, enable kernel‑mode Code Integrity (Hypervisor‑protected Code Integrity – HVCI) via:

Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\DeviceGuard\Scenarios\HypervisorEnforcedCodeIntegrity" -Name "Enabled" -Value 1

5. Simulating a BYOVD Attack (Authorized Lab Only)

To understand Qilin and Warlock’s technique, replicate it in an isolated VM.

Step‑by‑step guide:

  1. Download a known vulnerable driver (e.g., `DBUtil_2_3.sys` from a legit vendor) and a proof‑of‑concept exploit that calls ZwLoadDriver.
  2. Compile a DLL that will be side‑loaded – it should contain the driver installation code and a termination loop that iterates through 300+ EDR process names.
  3. Use a tool like `sc.exe` to create a kernel service pointing to the vulnerable driver: 
    sc create BadDrv binPath= C:\path\vuln.sys type=kernel
sc start BadDrv
  4. Once loaded, the exploit triggers the vulnerable IOCTL that grants arbitrary kernel read/write. Then the attacker can call `NtRaiseHardError` or directly `ZwTerminateProcess` on EDR processes.
  5. Mitigation test: Repeat steps with WDAC policy active – observe event 3076 blocking the load.

6. Linux & Cloud Hardening Parallels

While BYOVD is Windows‑specific, cloud and Linux environments face analogous “bring your own” kernel module risks.

Step‑by‑step guide:

  1. On Linux, enforce kernel module signing with `CONFIG_MODULE_SIG_FORCE=y` and block unsigned modules: 
    echo 1 > /proc/sys/kernel/modules_disabled  after loading required modules
  2. For AWS EC2, use Amazon Inspector to scan for exposed kernel vulnerabilities and apply CVE‑2024‑xxxx patches.
  3. For containers, drop `CAP_SYS_MODULE` to prevent module loading inside privileged containers: 
    docker run --cap-drop=ALL --cap-add=NET_ADMIN ...  no SYS_MODULE
  4. In Kubernetes, use OPA Gatekeeper to deny pods that request `CAP_SYS_MODULE` or mount /sys/kernel/security.

7. Post‑Exploitation Forensics: Identifying BYOVD in Your Environment

If you suspect a Qilin or Warlock breach, collect these artifacts.

Step‑by‑step guide:

  1. Collect the System event log for service start events (ID 7045) of non‑standard kernel drivers: 
    Get-WinEvent -FilterHashtable @{LogName='System'; ID=7045} | Where-Object {$_.Message -match ".sys"}
  2. Search for driver load times just before EDR process termination events (Event ID 4689 in Security log).
  3. Use PowerShell to find recently created `.sys` files in C:\Windows\System32\drivers: 
    Get-ChildItem C:\Windows\System32\drivers.sys | Where-Object {$_.CreationTime -gt (Get-Date).AddDays(-7)}
  4. Compute hashes and compare with VirusTotal or the loldrivers community blocklist: 
    Get-FileHash C:\Windows\System32\drivers\suspicious.sys -Algorithm SHA256

What Undercode Say:

  • Key Takeaway 1: BYOVD attacks are not theoretical; Qilin and Warlock have weaponized vulnerable drivers to kill over 300 EDR processes, rendering traditional endpoint protection useless without kernel‑level hardening.
  • Key Takeaway 2: Effective defense requires a layered approach: block vulnerable drivers via WDAC, monitor driver loads with Sysmon, and protect EDR processes with PPL and HVCI – no single control stops a determined attacker.

Analysis: The shift toward BYOVD marks a maturation of ransomware tactics. Attackers no longer bother with user‑land evasion; they go straight to the kernel, where security products are most exposed. Organizations that rely solely on signature‑based EDR are now at high risk. However, Microsoft has provided robust native tools (WDAC, HVCI, ASR rules) that, when properly configured, can neutralize BYOVD without third‑party costs. The catch is that many enterprises still disable these features due to compatibility fears. Qilin and Warlock exploit precisely that gap. Meanwhile, the underground economy for vulnerable drivers is booming – old, signed drivers from 2015 are resold as “EDR killers.” The only long‑term solution is a combination of driver blocklisting, process hardening, and a rapid incident response that assumes kernel compromise.

Prediction:

In the next 12 months, BYOVD will become a standard feature in all major ransomware families, including LockBit and BlackCat variants. Attackers will shift from reusing public vulnerable drivers to signing their own malicious drivers using stolen or forged certificates, bypassing simple hash‑based blocklists. Microsoft will respond by making HVCI and WDAC mandatory for Windows 12, but legacy Windows 10 installations will remain vulnerable. Furthermore, we will see cross‑platform BYOK (Bring Your Own Kernel) attacks targeting Linux eBPF and macOS system extensions. Blue teams must adopt proactive kernel integrity monitoring and automate the deployment of driver block rules using threat intelligence feeds – waiting for the next patch Tuesday will be fatal.

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Reported By: Hackermohitkumar Ransomware – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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