Petite12c1998IanLuck

Hunt Hypothesis

This detection identifies potential malicious activity associated with the specific YARA signature “Petite12c1998IanLuck,” which likely indicates a targeted file-based threat or known malware variant within the environment. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to validate its presence across endpoints, assess its impact on low-severity alerts, and ensure that existing defenses are effectively capturing this specific threat signature before it escalates into a broader incident.

YARA Rule

rule Petite12c1998IanLuck
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 66 9C 60 E8 CA 00 00 00 03 00 04 00 05 00 06 00 07 00 08 00 09 00 0A 00 0B 00 0D 00 0F 00 11 00 13 00 17 00 1B 00 1F 00 23 00 2B 00 33 00 3B 00 43 00 53 00 63 00 73 00 83 00 A3 00 C3 00 E3 00 02 01 00 00 00 00 00 00 00 00 00 00 00 00 01 01 01 01 02 02 02 }

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 Petite12c1998IanLuck detection rule, including suggested filters and exclusions:

• Scenario: Automated Endpoint Protection Scans by CrowdStrike Falcon or Microsoft Defender

  • Context: The YARA rule may flag the high-frequency file I/O and process spawning behavior of real-time anti-virus engines during their scheduled full-system scans. These tools often inject code into memory that mimics the signature pattern defined in Petite12c1998IanLuck.
  • Filter/Exclusion: Exclude processes where the executable path matches known AV binaries, such as C:\Program Files\CrowdStrike\FalconSensor\csfalcon.exe or C:\ProgramData\Microsoft\Windows Defender\platform\4.10.2308.9\MsMpEng.exe.

• Scenario: Scheduled PowerShell Script Execution for Patch Management

  • Context: During nightly maintenance windows, the IT team runs a scheduled Task (Task Scheduler) that executes a custom PowerShell script to deploy updates via SCCM or Intune. The script’s interaction with the .NET runtime and file system triggers the rule due to similar memory allocation patterns.
  • Filter/Exclusion: Create an exclusion for powershell.exe processes where the command line arguments contain specific keywords like -ExecutionPolicy Bypass -File "C:\Scripts\PatchDeploy.ps1" or if the parent process is svchost.exe running under the “Task Scheduler” service.

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

  • Context: The Microsoft Office Click-to-Run update mechanism (OfficeClickToRun.exe) frequently performs background updates and file integrity checks, which can generate network traffic and process behavior indistinguishable from the rule’s detection logic.