PEProtector093CRYPToCRACk

Hunt Hypothesis

This detection identifies potential ransomware or file encryption activities by leveraging a specific YARA signature that recognizes the behavioral patterns of the PEProtector093CRYPToCRACk indicator within executable files. Although currently flagged with low severity, proactive hunting for this signal in Azure Sentinel is essential to uncover early-stage encryption anomalies before they escalate into full-scale data exfiltration or system lockdown events.

YARA Rule

rule PEProtector093CRYPToCRACk
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 5B 81 E3 00 FF FF FF 66 81 3B 4D 5A 75 33 8B F3 03 73 3C 81 3E 50 45 00 00 75 26 0F B7 46 18 8B C8 69 C0 AD 0B 00 00 F7 E0 2D AB 5D 41 4B 69 C9 DE C0 00 00 03 C1 75 09 83 EC 04 0F 85 DD 00 00 }

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 PEProtector093CRYPToCRACk detection rule, along with recommended filters and exclusions:

• Scenario: Microsoft Office Document Encryption via PowerShell

  • Context: An admin runs a scheduled PowerShell job to encrypt sensitive HR documents stored in a shared network folder using the built-in System.Security.Cryptography library. The script iterates through files and applies AES-256 encryption, triggering the YARA rule due to the high volume of cryptographic API calls on PE executables.
  • Filter/Exclusion: Create an exclusion for the process path C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe when the command line contains keywords like -Command, “Encrypt”, or specific script paths (e.g., .\HR_Encryption.ps1). Alternatively, whitelist the hash of this specific scheduled task executable.

• Scenario: Antivirus Real-Time Scanning and Quarantine

  • Context: The enterprise endpoint protection suite (e.g., Microsoft Defender for Endpoint or CrowdStrike Falcon) performs real-time scanning on a large batch of newly downloaded software installers (.exe/.msi). During the scan, the AV engine decrypts and re-encrypts file headers to check for embedded malware, mimicking the behavior of a cryptoracker.
  • Filter/Exclusion: Exclude processes belonging to known security vendors from this rule. For example, filter out MsMpEng.exe (Microsoft Defender), C:\Program Files\CrowdStrike\fsqa.exe, or C:\Program Files\SentinelOne\SSO.exe. This prevents the AV engine’s own cryptographic operations from triggering alerts against itself.

• Scenario: Automated Backup Encryption with Veeam

  • Context: A nightly backup job initiated by Veeam Backup