VxXPEH4768

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging specific file-based malware signatures identified by the VxXPEH4768 YARA rule to establish a foothold within the environment. Proactive hunting in Azure Sentinel is essential because the low-severity classification may cause these initial infection indicators to be overlooked during routine monitoring, allowing attackers to persist undetected before escalating their activities.

YARA Rule

rule VxXPEH4768
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 [2] 5B 81 [3] 50 56 57 2E [5] 2E [6] B8 01 00 50 B8 [2] 50 E8 }

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 VxXPEH4768 detection rule, including suggested filters and exclusions tailored for a legitimate enterprise environment:

• Scenario: Antivirus Engine Self-Scanning

  • Context: The endpoint protection agent (e.g., CrowdStrike Falcon or Microsoft Defender) scans its own update binaries during the nightly maintenance window. These binaries often contain embedded signatures that match the YARA pattern for “malicious files associated.”
  • Filter/Exclusion: Exclude processes where ProcessName matches *defender.exe, *falcon.sysmon.exe, or *ccSvcHst.exe AND the file path contains \Program Files\Microsoft Defender\ or \CrowdStrike\Falcon.

• Scenario: Scheduled Software Deployment via SCCM/Intune

  • Context: System Center Configuration Manager (SCCM) or Microsoft Intune pushes a major application update (e.g., Adobe Acrobat Pro or Zoom) during business hours. The deployment engine extracts compressed archives containing installer executables that trigger the rule due to their high entropy and embedded resources.
  • Filter/Exclusion: Create an exclusion for files located in temporary deployment folders, specifically paths starting with C:\Windows\CCM\Cache\ or C:\ProgramData\Microsoft\IntuneManagementExtension\, where the parent process is ccmsetup.exe or Win32App.exe.

• Scenario: Automated Backup and Archiving Jobs

  • Context: A nightly backup job using Veeam Agent or Acronis Cyber Protect compresses large datasets into .zip or .7z archives. The YARA rule flags the archive headers and internal metadata structures as suspicious due to their complex binary composition resembling packed malware.
  • Filter/Exclusion: Exclude events where `FileName