PENinjav10DzAkRAkerTNT

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging specific file signatures identified by the PENinjav10DzAkRAkerTNT YARA rule to detect early-stage malware or suspicious artifacts that may evade standard signature-based defenses. Proactively hunting for these indicators in Azure Sentinel allows the SOC team to identify low-severity anomalies before they escalate, ensuring comprehensive visibility into potential threats that might otherwise be overlooked by automated alerting thresholds.

YARA Rule

rule PENinjav10DzAkRAkerTNT
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BE 5B 2A 40 00 BF 35 12 00 00 E8 40 12 00 00 3D 22 83 A3 C6 0F 85 67 0F 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 }

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 PENinjav10DzAkRAkerTNT detection rule, including suggested filters and exclusions:

• Scenario: Microsoft Defender Antivirus Real-Time Scan

  • Context: The YARA signature matches the behavior of MsMpEng.exe (Microsoft Defender) when it scans large archives or updates its definition database, which often involves unpacking nested structures similar to the rule’s logic.
  • Filter/Exclusion: Exclude processes where the executable path is C:\Program Files\Windows Defender\MsMpEng.exe and the parent process is MsMpEng.exe.

• Scenario: Scheduled Office 365 Click-to-Run Update

  • Context: The rule triggers during the daily automated update cycle of Microsoft Office, where OfficeC2RClient.exe extracts temporary installation packages that mimic the file structure detected by PENinjav10DzAkRAkerTNT.
  • Filter/Exclusion: Create an exclusion for processes named OfficeC2RClient.exe running under the user context of SYSTEM or a dedicated service account (e.g., DOMAIN\svc-office-updates).

• Scenario: Endpoint Detection and Response (EDR) Agent Scans

  • Context: CrowdStrike Falcon or Carbon Black agents perform deep file integrity checks on critical system directories, generating memory signatures that overlap with the rule’s detection logic.
  • Filter/Exclusion: Exclude events where the parent process is C:\Program Files\CrowdStrike\FalconSensor\csfalcon.exe (or equivalent EDR agent path) and the action is “Scan” or “Integrity Check”.

• Scenario: Automated Backup Job via Veeam

  • Context: During nightly backup windows, `Vee