VxHaryanto

Hunt Hypothesis

This hypothesis targets the execution of the VxHaryanto malware family, a known threat actor tool often used for initial access or lateral movement in enterprise environments. Proactively hunting for this signature allows the SOC to identify compromised hosts early, potentially before the adversary establishes persistence or exfiltrates data within the Azure Sentinel environment.

YARA Rule

rule VxHaryanto
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 81 EB 2A 01 8B 0F 1E 5B 03 CB 0E 51 B9 10 01 51 CB }

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

• Legacy Java Application Deployment: A development team deploys a legacy Java-based enterprise application (e.g., an internal ERP module or middleware) that bundles an older version of the Java Runtime Environment (JRE) or uses specific native libraries with known byte patterns matching the VxHaryanto signature.
  • Filter/Exclusion: Exclude files located in standard application directories (e.g., C:\Program Files\MyLegacyApp\lib\ or C:\opt\legacy-app\) and filter by file extension .jar or .so/.dll if the rule targets specific library types.
• Third-Party SDK Integration: An engineering team integrates a third-party C++ or C# SDK (e.g., for video processing, encryption, or database connectivity) that contains static linking artifacts or specific function prologues that trigger the YARA pattern.
  • Filter/Exclusion: Exclude binaries from known vendor SDK paths (e.g., C:\Program Files (x86)\VendorSDK\bin\) and whitelist specific DLL names (e.g., vendor_core.dll) after verifying the hash matches the approved vendor distribution.
• Scheduled Backup Utility: A nightly scheduled task runs a proprietary backup utility (e.g., backup_agent.exe) that uses a custom compression algorithm or memory mapping technique that coincidentally matches the VxHaryanto heuristic.
  • Filter/Exclusion: Exclude the specific executable path (e.g., C:\ProgramData\BackupTools\backup_agent.exe) and filter by process name backup_agent.exe if the rule is process-based, or exclude the file hash if it is file-based.
• Development Environment Artifacts: Developers compile local test projects or debug builds in shared network drives or local user directories, resulting in unoptimized binaries with debug symbols or specific stack layouts that trigger the detection