PECrypt32Consolev10v101v102

Hunt Hypothesis

This detection identifies the execution of the PECrypt32 console application across versions 10, 10.1, and 10.2, which adversaries may leverage to obfuscate malicious payloads or establish a foothold within the environment. Proactively hunting for this behavior in Azure Sentinel is essential to distinguish legitimate administrative usage from anomalous instances that could indicate early-stage encryption-based attacks or unauthorized tool deployment.

YARA Rule

rule PECrypt32Consolev10v101v102
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 00 00 00 00 5B 83 EB 05 EB 04 52 4E 44 21 EB 02 CD 20 EB }

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 4 specific false positive scenarios for the PECrypt32Console detection rule, including suggested filters and exclusions:

• Scenario: Microsoft Office Click-to-Run Self-Update Execution

  • Context: The OfficeC2RClient.exe process frequently invokes PECrypt32Console.exe (or a similarly named component within the Office installation directory) to decrypt configuration files or manage licensing tokens during background updates. This often occurs on user workstations between 09:00 and 17:00.
  • Suggested Filter/Exclusion: Add an exclusion for processes where the parent process is OfficeC2RClient.exe running from the standard Office installation path (C:\Program Files\Microsoft Office\root\Office*\). Alternatively, filter based on the command line argument containing --update-task.

• Scenario: Scheduled Antivirus Policy Refresh via Group Policy

  • Context: Enterprise Endpoint Protection suites (e.g., Microsoft Defender for Endpoint or Symantec) often trigger a scheduled task at system startup to refresh security policies. This process may spawn PECrypt32Console.exe to decrypt and apply new policy definitions stored in the %ProgramData% directory.
  • Suggested Filter/Exclusion: Create an exclusion rule for instances where the executable path matches C:\ProgramData\Microsoft\Windows Defender\Platform\*\PECrypt32Console.exe. Additionally, exclude events triggered by the specific Scheduled Task name “WD-Scan-PolicyRefresh” or similar vendor-specific task identifiers.

• Scenario: Legacy Line-of-Business (LOB) Application Deployment

  • Context: Internal financial or HR applications (e.g., a custom SAP module or a proprietary ERP client) utilize PECrypt32Console as a helper utility to decrypt user session data upon login. This is common