AHTeamEPProtector03fakePECrypt102FEUERRADER

Hunt Hypothesis

This rule identifies potentially obfuscated or packed executables that may be used by adversaries to hide malicious code and evade static analysis during initial access or execution phases. Proactively hunting for these artifacts in Azure Sentinel helps detect low-fidelity threats that might slip past signature-based defenses, ensuring early identification of suspicious payloads before they establish a foothold in the environment.

YARA Rule

rule AHTeamEPProtector03fakePECrypt102FEUERRADER
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 90 [46] 90 FF E0 E8 00 00 00 00 5B 83 EB 05 EB 04 52 4E 44 }

condition:
		$a0 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Antivirus/EDR Self-Extraction and Scanning: Security agents like CrowdStrike Falcon, Microsoft Defender for Endpoint, or Trend Micro often extract or temporarily create PE files in memory or disk during real-time scanning, heuristic analysis, or signature updates. These temporary artifacts may retain specific header patterns or encryption stubs that match the YARA rule.

  • Filter/Exclusion: Exclude processes where the parent process is a known security agent (e.g., FalconSensor.exe, MsMpEng.exe, TmService.exe) or exclude file paths within the agent’s temporary working directories (e.g., C:\ProgramData\CrowdStrike\, C:\ProgramData\Microsoft\Windows Defender\).

• Software Installer and Update Services: Major enterprise applications such as Adobe Creative Cloud, JetBrains Toolbox, or Visual Studio use custom installers that may embed or extract PE components with non-standard headers or lightweight encryption for integrity checks. Scheduled update jobs (e.g., AdobeUpdateService, JetBrainsUpdater) frequently trigger this during nightly maintenance windows.

  • Filter/Exclusion: Exclude processes initiated by known installer services (e.g., MsiExec.exe with specific parent chains, AdobeUpdateService.exe) or exclude file paths under C:\Program Files\Adobe\, C:\Users\<User>\AppData\Local\JetBrains\, or C:\Program Files (x86)\Common Files\.

• Java/.NET Runtime JAR-to-PE Conversion: Applications built on Java (JRE/JDK) or .NET Core (e.g., Eclipse IDE, IntelliJ IDEA, Spring Boot apps) may use tools like jpackage or dotnet publish to generate self-contained executables. These generated PEs can have atypical