Pe123v2006412

Hunt Hypothesis

This hunt hypothesis targets the presence of specific executable artifacts identified by the Pe123v2006412 YARA signature to detect potential early-stage malware or suspicious application behavior within the Azure Sentinel environment. Proactively hunting for this indicator allows the SOC team to identify low-severity anomalies that may represent initial footholds or lateral movement attempts before they escalate into critical incidents, ensuring comprehensive coverage of known threat patterns.

YARA Rule

rule Pe123v2006412
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 8B C0 60 9C E8 01 00 00 00 C3 53 E8 72 00 00 00 50 E8 1C 03 00 00 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 8B 7D 0C 8B 75 08 F3 A4 61 5D C2 0C 00 E8 00 00 00 00 58 83 E8 05 C3 8B C0 E8 00 00 00 00 58 83 C0 05 C3 8B }

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

False Positive Scenarios for Rule Pe123v2006412

• Scenario: Microsoft Office 365 Click-to-Run Updates

  • Context: The YARA rule detects the execution of OfficeClickToRun.exe or related processes (e.g., MsoClientTask.exe) during scheduled update windows. These legitimate background tasks often spawn child processes with similar PE headers that match the signature logic, triggering alerts when users are actively editing documents.
  • Suggested Filter: Exclude process paths containing \Microsoft Office ClickToRun\ and filter out events where the parent process is OfficeClickToRun.exe.
    • Example Logic: ProcessPath contains "C:\Program Files\Common Files\microsoft shared\ClickToRun" AND ParentImageName == "OfficeClickToRun.exe"

• Scenario: Antivirus Engine Scanning (CrowdStrike Falcon / Defender)

  • Context: During peak business hours, the endpoint protection suite (e.g., CrowdStrike Falcon Sensor or Windows Defender) performs real-time scanning of user-generated files. The rule may flag the falcon.sys or MsMpEng.exe processes as they inject code into user sessions to scan specific document types that match the YARA pattern.
  • Suggested Filter: Create an exclusion for known security vendor executables and their associated service accounts (e.g., CRONOS, SYSTEM).
    • Example Logic: ProcessImageName IN ("falcon.sys", "MsMpEng.exe") AND AccountName IN ("SYSTEM", "Network Service", "CRONOS")

• Scenario: Scheduled PowerShell Backup Jobs

  • Context: An enterprise-wide scheduled task runs nightly or hourly to archive logs and documents using powershell.exe. When these scripts invoke external tools (like 7