XPack152164

Hunt Hypothesis

This YARA rule detects specific file patterns or memory artifacts associated with the XPack152164 signature, potentially indicating the presence of a known malware family or suspicious executable behavior. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify low-severity threats early in the kill chain, reducing the risk of lateral movement or privilege escalation before they escalate in severity.

YARA Rule

rule XPack152164
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 8B EC FA 33 C0 8E D0 BC [2] 2E [4] 2E [4] EB }

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

• Legitimate Backup/Archive Operations: Enterprise backup solutions like Veeam Backup & Replication or Commvault often create large, compressed archive files (e.g., .vbk, .zip, .tar) that may contain specific byte patterns or entropy levels triggering generic YARA signatures.
  • Filter/Exclusion: Exclude file paths under standard backup directories (e.g., C:\Program Files\Veeam\, \\backup-server\archives\) or exclude file extensions known to be archives (.zip, .tar, .7z, .vbk) if the rule is primarily targeting executable code.
• Software Installer Extraction: When IT administrators deploy software via Microsoft Endpoint Configuration Manager (MECM/SCCM) or Intune, installers (.msi, .exe) are frequently extracted to temporary directories (%TEMP%, C:\Windows\Installer\) for installation. These extracted binaries may match YARA patterns designed to catch obfuscated payloads.
  • Filter/Exclusion: Exclude processes or file paths associated with known installer services (e.g., msiexec.exe, wuaexhost.exe) or files located in C:\Windows\Installer\ and C:\ProgramData\Package Cache\.
• Java/.NET Runtime Compilation: Applications using Java (JVM) or .NET (JIT compiler) dynamically generate intermediate bytecode or native images in memory or temporary disk locations. This dynamic code generation can sometimes exhibit characteristics that trigger YARA rules looking for packed or obfuscated executables.
  • Filter/Exclusion: Exclude files or processes associated with java.exe, dotnet.exe, or mscorwks.dll/clrjit.dll, and specifically exclude paths like C:\Program Files\Java\ or `C:\Program Files\dotnet\