SimplePack V11X Method2 bagie additional

Hunt Hypothesis

This hypothesis targets the execution of SimplePack, a known malware loader that utilizes specific packing methods to obscure its payload and evade static analysis. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify early-stage compromise attempts where adversaries deploy this loader to establish persistence or download secondary payloads before full-blown ransomware or trojan activity manifests.

YARA Rule

rule SimplePack_V11X_Method2_bagie_additional: PEiD
{
    strings:
        $a = { 4D 5A 90 EB 01 00 52 E9 89 01 00 00 50 45 00 00 4C 01 02 00 00 00 00 00 00 00 00 00 00 00 00 00 E0 00 0F 03 0B 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0C 00 00 00 00 ?? ?? ?? 00 10 00 00 00 02 00 00 01 00 00 00 00 00 00 00 04 00 00 00 00 00 00 00 }
    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 manually compiles a lightweight C/C++ utility using the SimplePack compiler (V11X) to create a portable, dependency-free executable for quick testing or debugging on a build server.
  • Filter/Exclusion: Exclude files located in specific development directories (e.g., C:\Dev\Projects\*, C:\Builds\*) or exclude if the parent process is a known compiler/IDE executable (e.g., cl.exe, gcc.exe, code.exe).
• Scenario: An IT administrator uses a custom internal tooling script that leverages SimplePack V11X to package a small configuration management agent or health-check script for deployment to edge devices, where the resulting .exe is copied to a standard C:\Program Files\InternalTools\ directory.
  • Filter/Exclusion: Exclude files with a known hash list of approved internal tools, or exclude if the file path matches C:\Program Files\InternalTools\* and the file size is under a specific threshold (e.g., < 500KB).
• Scenario: A scheduled maintenance job (e.g., Task Scheduler entry “DailyLogCompressor”) executes a small, self-contained executable built with SimplePack to compress and archive log files in C:\Logs\Archived\, which is a common pattern for lightweight, stateless utilities.
  • Filter/Exclusion: Exclude if the parent process is svchost.exe (for scheduled tasks) or TaskScheduler.exe, and the file path is within a designated log/archive directory (e.g., C:\Logs\*, C:\Archives\*).
• Scenario: A security team deploys a lightweight, read-only EDR sensor or integrity checker built with SimplePack to a ring of test VM