Deconstructing EDR Evasion: A Practical Guide for Threat Hunters

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Introduction

Endpoint Detection and Response (EDR) evasion techniques are increasingly used by threat actors to bypass security controls. However, understanding these methods can empower defenders to detect and mitigate attacks more effectively. Sai M.’s upcoming workshop, “Deconstructing the EDR Evasion Mille-Feuille: a LAYER-Based Framework,” provides hands-on techniques to turn evasion attempts into detection opportunities.

Learning Objectives

  • Understand common EDR evasion techniques and their underlying mechanisms.
  • Learn how to hunt threat actors by analyzing evasion patterns.
  • Develop detection rules for EDR bypass methods using SIEM tools like Sentinel, Splunk, and Elastic.

You Should Know

1. Detecting Process Hollowing

Command (Windows):

Get-WmiObject -Query "SELECT  FROM Win32_Process WHERE Name = 'svchost.exe' AND CommandLine LIKE '% -k %'" | Select-Object ProcessId, CommandLine

What it does:

Process hollowing is a technique where malware replaces legitimate process memory with malicious code. This PowerShell query identifies suspicious `svchost.exe` instances with unusual command-line arguments.

Steps:

  1. Run the command in an elevated PowerShell session.
  2. Review the output for `svchost.exe` processes with unexpected `-k` parameters.
  3. Investigate anomalous processes using tools like Process Explorer or Sysinternals.

2. Hunting for Reflective DLL Injection

Command (Linux – Volatility):

vol.py -f memory.dump malfind --output=json

What it does:

Reflective DLL injection loads a malicious DLL without touching disk. Volatility’s `malfind` plugin detects anomalous memory regions.

Steps:

  1. Acquire a memory dump using tools like `LiME` or WinPmem.
  2. Run the command to scan for suspicious memory allocations.
  3. Cross-reference findings with EDR logs for further validation.

3. Identifying API Unhooking

Command (Windows – Sysmon):

<EventFilter>
<RuleGroup name="API Unhooking Detection">
<ProcessAccess TargetImage="C:\Windows\System32\ntdll.dll" GrantedAccess="0x1F0FFF"/> 
</RuleGroup> 
</EventFilter>

What it does:

API unhooking bypasses EDR by restoring hooked functions. This Sysmon rule monitors access to `ntdll.dll` with excessive permissions.

Steps:

1. Add the rule to your Sysmon configuration.

  1. Monitor Event ID 10 (Process Access) for suspicious activity.
  2. Correlate with endpoint logs to confirm malicious behavior.

4. Detecting AMSI Bypass

Command (PowerShell):

Get-WinEvent -FilterHashtable @{LogName='Microsoft-Windows-PowerShell/Operational'; ID=4104} | Where-Object { $_.Message -match "amsiinitfailed" }

What it does:

AMSI bypass techniques disable script scanning. This query checks PowerShell logs for AMSI initialization failures.

Steps:

  1. Run the command to review PowerShell operational logs.
  2. Investigate any `amsiinitfailed` events for potential bypass attempts.

3. Block malicious scripts using application whitelisting.

5. Cloud Hardening: Restricting Unused IAM Permissions

Command (AWS CLI):

aws iam generate-credential-report 
aws iam get-credential-report --output text > report.csv

What it does:

Overly permissive IAM roles are a common attack vector. This command generates an AWS credential report for auditing.

Steps:

1. Run the commands to export IAM permissions.

2. Analyze `report.csv` for unused or excessive permissions.

  1. Apply the principle of least privilege (PoLP) to reduce risk.

What Undercode Say

  • Key Takeaway 1: EDR evasion techniques are not undetectable—they often leave artifacts that can be leveraged for hunting.
  • Key Takeaway 2: Proactive detection requires understanding attacker tradecraft and adapting defensive strategies.

Analysis:

The rise in EDR evasion highlights the need for layered defenses. By studying evasion methods, defenders can preemptively build detections and reduce attacker dwell time. Workshops like DEATHCon 2025 provide critical hands-on experience for staying ahead of adversaries.

Prediction

As EDR solutions evolve, attackers will develop more sophisticated bypass techniques. However, integrating behavioral analytics and threat intelligence will enable defenders to detect even the most advanced evasion attempts. The future of threat hunting lies in continuous learning and collaboration across the cybersecurity community.

Additional Resources:

IT/Security Reporter URL:

Reported By: Activity 7342074963811553280 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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