Pe123v200644

Hunt Hypothesis

This hypothesis targets the presence of specific executable artifacts identified by the YARA rule Pe123v200644, which may indicate the deployment of custom malware or known threat actor tooling within the environment. Proactively hunting for these signatures allows the SOC team to identify low-severity footholds or early-stage intrusions before they escalate into more impactful lateral movement or data exfiltration activities.

YARA Rule

rule Pe123v200644
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 8B C0 EB 01 34 60 EB 01 2A 9C EB 02 EA C8 E8 0F 00 00 00 EB 03 3D 23 23 EB 01 4A EB 01 5B C3 8D 40 00 53 EB 01 6C EB 01 7E EB 01 8F E8 15 01 00 00 50 E8 67 04 00 00 EB 01 9A 8B D8 FF D3 5B C3 8B C0 E8 00 00 00 00 58 83 C0 05 C3 8B C0 55 8B EC 60 8B 4D 10 }

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

• Antivirus/EDR Self-Scan or Update: When the endpoint protection agent (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne) performs a full disk scan or updates its signature database, it may load PE files into memory or create temporary copies that match the generic Pe123v200644 YARA pattern.
  • Filter/Exclusion: Exclude processes where the parent process is the AV/EDR service (e.g., CsfalconService.exe, MsMpEng.exe, SentinelOneAgent.exe) or exclude file paths located in the vendor’s specific installation directory (e.g., C:\Program Files\CrowdStrike\).
• Legacy Application Installer Execution: Enterprise environments often run legacy installers (e.g., older versions of Adobe Creative Suite, Oracle Java, or .NET Framework updates) that use custom PE structures or packing techniques that inadvertently match the Pe123v200644 heuristic.
  • Filter/Exclusion: Exclude execution of files with .msi, .exe, or .setup extensions located in standard installer directories (e.g., C:\Program Files (x86)\Common Files\InstallShield\, C:\Windows\Installer\) or where the command line contains msiexec /i or /qn.
• Scheduled Backup or Archiving Jobs: Scheduled tasks (e.g., Veeam, Commvault, or Windows Server Backup) that process large volumes of PE files (executables, DLLs) for compression or deduplication may trigger the rule if the YARA scan inspects the raw binary structure during the I/O operation.
  • Filter/Exclusion: Exclude processes associated with backup agents (e.g., VeeamBackup.exe, CommvaultClient.exe) or exclude