Reg2Exe224byJanVorel

Hunt Hypothesis

This hunt hypothesis targets adversaries who leverage specific registry-to-executable patterns to establish persistence or execute malicious payloads within Windows environments. Proactively hunting for this behavior in Azure Sentinel is essential to identify early-stage indicators of compromise that may be missed by standard alerting due to the rule’s low severity classification.

YARA Rule

rule Reg2Exe224byJanVorel
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 6A 00 E8 CF 20 00 00 A3 F4 45 40 00 E8 CB 20 00 00 6A 0A 50 6A 00 FF 35 F4 45 40 00 E8 07 00 00 00 50 E8 BB 20 00 00 CC 68 48 00 00 00 68 00 00 00 00 68 F8 45 40 00 E8 06 19 00 00 83 C4 0C 8B 44 24 04 A3 FC 45 40 00 68 00 00 00 00 68 A0 0F 00 00 68 00 00 00 00 E8 8C 20 00 00 A3 F8 45 40 00 E8 02 20 00 00 E8 32 1D 00 00 E8 20 19 00 00 E8 A3 16 00 00 68 01 00 00 00 68 38 46 40 00 68 00 00 00 00 8B 15 38 46 40 00 E8 71 4F 00 00 B8 00 00 10 00 BB 01 00 00 00 E8 82 4F 00 00 FF 35 48 41 40 00 B8 00 01 00 00 E8 9D 15 00 00 8D 0D 1C 46 40 00 5A E8 82 16 00 00 68 00 01 00 00 FF 35 1C 46 40 00 E8 24 20 00 00 A3 24 46 40 00 FF 35 48 41 40 00 FF 35 24 46 40 00 FF 35 1C 46 40 00 E8 DC 10 00 00 8D 0D 14 46 40 00 5A E8 4A 16 }

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

Here are 5 specific false positive scenarios for the Reg2Exe224byJanVorel detection rule, focusing on legitimate enterprise activities that mimic the behavior of registry-to-execution anomalies:

• Scenario: Microsoft Endpoint Configuration Manager (SCCM) Software Updates

  • Context: SCCM often modifies registry keys to trigger software deployments or patch installations. When a client agent reads these new registry entries and launches the associated installer executable, it can trigger this rule.
  • Filter/Exclusion: Exclude processes where the parent is ccmexec.exe (Configuration Manager Client) and the executed file path contains \Microsoft Update\ or \SoftwareDistribution\. Additionally, filter out executions occurring during defined maintenance windows (e.g., 02:00–04:00 local time).

• Scenario: Group Policy Object (GPO) Startup Scripts

  • Context: Administrators frequently configure GPOs to run specific batch scripts or executables at user logon. These scripts often read registry settings defined in the policy and then launch a utility tool, creating a “Registry -> Executable” chain that matches the rule’s logic.
  • Filter/Exclusion: Create an exclusion for processes spawned by gpupdate.exe or userinit.exe. Specifically, filter out executions where the command line contains -script parameters pointing to standard administrative paths like %SystemDrive%\Windows\System32\GroupPolicy\Machine\Scripts\Startup\.

• Scenario: Antivirus Definition Updates (e.g., CrowdStrike or SentinelOne)

  • Context: Endpoint Detection and Response (EDR) agents frequently check registry keys for update schedules. Upon detecting a new definition version in the registry, they immediately launch their updater service to download and apply patches. This rapid sequence is a common trigger for this rule.