PE Protect 09

Hunt Hypothesis

This rule identifies Windows executables that utilize specific PE header protections or obfuscation techniques, which adversaries often employ to hinder static analysis and evade signature-based detection. Proactively hunting for these artifacts in Azure Sentinel allows the SOC to uncover potentially malicious or stealthy binaries that may have bypassed initial perimeter defenses and are executing within the environment.

YARA Rule

rule PE_Protect_09: PEiD
{
    strings:
        $a = { E9 ?? 00 00 00 0D 0A 0D 0A C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 C4 0D 0A 50 45 2D 50 52 4F 54 45 43 54 20 30 2E 39 20 28 43 29 6F }
    condition:
        $a 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

• Scenario: A developer or DevOps engineer uses PEBakery or PEBakery GUI to add a standard PE header (e.g., .text, .data) to a custom utility or test binary before deploying it to a staging environment.

  • Filter/Exclusion: Exclude files located in specific development directories (e.g., C:\Dev\Projects\ or C:\Users\<User>\AppData\Local\Temp\) where the parent process is a known IDE or build tool (e.g., msbuild.exe, dotnet.exe, code.exe).

• Scenario: An IT administrator runs HxD or 010 Editor to manually patch a legacy application’s PE header to fix a compatibility issue or remove a specific section (e.g., .rsrc) before redistributing it via Group Policy or a deployment script.

  • Filter/Exclusion: Exclude files modified by known hex editors (e.g., hxeditor.exe, 010editor.exe) or where the file path contains keywords like _patched, _fixed, or _deploy in the filename.

• Scenario: A scheduled maintenance job using 7-Zip or WinRAR extracts a compressed archive containing a PE file that was previously compressed with a tool that preserves or modifies certain PE attributes (e.g., stripping debug info), triggering the rule upon extraction.

  • Filter/Exclusion: Exclude PE files created by archive extraction processes (e.g., 7z.exe, winrar.exe) where the file age is less than 5 minutes and the source path is a known archive location (e.g., C:\Archives\, C:\Deployments\).

• Scenario: A software vendor’s installer (e.g., NSIS, Inno Setup, or **Wi