The Evolving EDR Landscape
Endpoint Detection and Response (EDR) solutions have become the cornerstone of modern enterprise security. However, as these tools evolve, so do the techniques used to bypass them.
During a recent Purple Team engagement for a Fortune 500 financial services client, our operators identified several methods that allowed us to operate undetected for extended periods. This article shares our findings – not as a blueprint for attackers, but as critical intelligence for defenders.
Common Evasion Techniques We Observed
1. Living Off the Land (LOLBins)
Attackers increasingly leverage legitimate Windows binaries to execute malicious payloads:
| Binary | MITRE ATT&CK | Use Case |
|---|---|---|
mshta.exe |
T1218.005 | Execute HTA files with embedded scripts |
regsvr32.exe |
T1218.010 | Execute scriptlets from URL (“Squiblydoo”) |
certutil.exe |
T1105, T1140 | Download and decode payloads |
2. Memory-Only Payloads
By keeping malicious code entirely in memory and never touching disk, attackers can evade signature-based detection:
- Reflective DLL Injection (T1055.001) – Load DLL without Windows Loader
- Process Hollowing (T1055.012) – Replace legitimate process memory
3. API Unhooking (T1562.001)
Modern EDR solutions hook Windows APIs to monitor process behavior. Sophisticated attackers can “unhook” these by reading clean copies of DLLs from disk, rendering user-mode monitoring blind.
Defensive Recommendations
- Implement behavioral analytics beyond signature matching
- Monitor for LOLBin abuse with custom detection rules
- Enable memory protection features like Credential Guard
- Conduct regular Purple Team exercises to validate your controls
Conclusion
The cat-and-mouse game between attackers and defenders continues. The key is not to rely on any single tool, but to build defense-in-depth with continuous validation through offensive testing.
Want to test your EDR’s effectiveness? Contact our Red Team for a Purple Team engagement.
