PseudoSigner01WATCOMCCEXEAnorganix

Hunt Hypothesis

This detection identifies potentially malicious or suspicious executables that utilize a specific pseudo-signature pattern associated with WATCOM compiler artifacts, which may indicate an adversary attempting to evade standard signature-based defenses through obfuscation. Proactively hunting for these anomalies in Azure Sentinel is critical because low-severity pseudo-signed binaries often serve as early indicators of sophisticated supply chain compromises or living-off-the-land attacks that could bypass initial automated alerts.

YARA Rule

rule PseudoSigner01WATCOMCCEXEAnorganix
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E9 00 00 00 00 90 90 90 90 57 41 E9 }

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 PseudoSigner01WATCOMCCEXEAnorganix detection rule, including suggested filters and exclusions:

• Scenario: Legacy ERP Data Migration via WATCOM C Compiler Binaries

  • Context: During scheduled nightly data migrations, the enterprise’s legacy ERP system (e.g., SAP or Oracle EBS) utilizes custom executables compiled with the WATCOM C compiler. These binaries often lack a standard code signing certificate or use an internal “Anorganix” pseudo-signer for internal validation, triggering the rule when they execute batch jobs on file servers.
  • Filter/Exclusion: Create a whitelist exclusion based on the specific process path and hash.
    • Action: Exclude C:\Program Files\LegacyERP\Bin\WATCOM_Migration.exe (Hash: SHA256-...) from detection if the parent process is msbuild.exe or a known service account (DOMAIN\svc_migration).

• Scenario: Automated Build Pipeline Execution in Dev/Test Environments

  • Context: In the CI/CD pipeline (e.g., Jenkins or Azure DevOps), build agents compile internal microservices using WATCOM C toolchains. The resulting executable artifacts are temporarily signed with an “Anorganix” pseudo-signer before being promoted to production, causing alerts during the compilation and unit testing phases on build nodes.
  • Filter/Exclusion: Implement a context-based filter targeting specific host groups or user accounts involved in development.
    • Action: Suppress alerts for this rule when the source machine belongs to the BUILD_AGENTS AD group OR when the running user is SYSTEM on hosts tagged with “Dev-Test”.

• Scenario: Third-Party Inventory Management Software Updates

  • Context: A specialized