HEALTHv51byMuslimMPolyak

Hunt Hypothesis

This YARA rule targets specific memory patterns associated with the HEALTHv51byMuslimMPolyak signature, potentially indicating the presence of a low-severity malware variant or a benign file with anomalous characteristics. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify early-stage infections or false positives in endpoint memory, ensuring rapid triage and validation of low-fidelity alerts before they escalate.

YARA Rule

rule HEALTHv51byMuslimMPolyak
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 1E E8 [2] 2E 8C 06 [2] 2E 89 3E [2] 8B D7 B8 [2] CD 21 8B D8 0E 1F E8 [2] 06 57 A1 [2] 26 }

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

• Scenario: A legacy Java-based Enterprise Resource Planning (ERP) system (e.g., SAP NetWeaver or Oracle E-Business Suite) running on a Windows server utilizes a specific version of the Java HotSpot VM. The YARA rule likely matches a known memory pattern or class file structure in the java.exe process or its associated DLLs (e.g., jvm.dll) that is common in older JDK versions (1.7 or 1.8) still maintained for compatibility.

  • Filter/Exclusion: Exclude processes where the executable path matches C:\Program Files\Java\jre1.8.0*\bin\java.exe or C:\Program Files (x86)\Java\jre1.8.0*\bin\java.exe, and ensure the parent process is a known service host (e.g., services.exe or svchost.exe) rather than an interactive user session.

• Scenario: A .NET-based internal business application (e.g., a custom inventory management tool) uses the System.Data.OleDb provider to connect to a legacy SQL Server 2008 instance. The YARA rule may be triggering on the specific byte sequence of the msado15.dll or sqlncli11.dll driver loaded into the application’s memory space, which contains a known signature pattern that overlaps with the rule’s heuristic.

  • Filter/Exclusion: Exclude alerts where the process name is a known .NET executable (e.g., MyApp.exe, dotnet.exe, or w3wp.exe for IIS-hosted apps) and the loaded module list includes sqlncli*.dll or msado*.dll. Verify the application is signed by the internal Code Signing certificate.

• Scenario: A scheduled maintenance job runs a PowerShell script that invokes `cscript