Vx Eddie2000

Hunt Hypothesis

This hypothesis targets the presence of the Vx_Eddie2000 malware variant, which may indicate an adversary has established a foothold or is executing specific malicious payloads within the environment. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify low-severity threats early, preventing potential lateral movement or data exfiltration before they escalate into a larger incident.

YARA Rule

rule Vx_Eddie2000: PEiD
{
    strings:
        $a = { E8 ?? ?? 5E 81 EE ?? ?? FC 2E ?? ?? ?? ?? 2E ?? ?? ?? ?? 4D 5A ?? ?? FA 8B E6 81 C4 ?? ?? FB 3B ?? ?? ?? ?? ?? 50 06 56 1E 8B FE 33 C0 50 8E D8 C5 ?? ?? ?? B4 30 CD 21 }
    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 legacy Java-based enterprise application (e.g., an older version of SAP GUI or a custom internal tool) uses a specific bytecode pattern or string constant that matches the Vx_Eddie2000 YARA signature due to shared library dependencies or similar code structures.

  • Filter/Exclusion: Exclude files located in the application’s specific installation directory (e.g., C:\Program Files\LegacyApp\bin\) or exclude executable files with a specific version number range if the YARA rule targets a known version of the Java runtime or a specific JAR file hash.

• Scenario: A standard Windows scheduled task runs a PowerShell script or a small C# executable (e.g., BackupHelper.exe) that is compiled with a specific .NET framework version or contains a unique string identifier (like a GUID or license key) that coincidentally matches the byte sequence targeted by the YARA rule.

  • Filter/Exclusion: Exclude processes or files where the parent process is Task Scheduler (svchost.exe with SchedSvc service) and the file path is within the scheduled task’s working directory (e.g., C:\ProgramData\CorporateTasks\), or exclude files with a specific digital signature from the internal CA.

• Scenario: A developer or IT admin copies a test binary or a specific version of a third-party utility (e.g., 7z.exe or WinRAR.exe) to a temporary folder (C:\Temp\ or %USERPROFILE%\Downloads\) for manual testing or distribution, and the file’s specific build or patch level triggers the YARA match.

  • Filter/Exclusion: Exclude files located in common temporary or download directories (C:\Temp\, C:\Users\*\Downloads\, C:\Users\*\AppData\Local\Temp\) unless