Look for DCP Des EncryptECB

Hunt Hypothesis

The DCP Des EncryptECB rule detects potential use of the Data Cryptography Provider (DCP) with the DES algorithm in ECB mode, which may indicate legacy encryption methods used in malicious activities. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential data exfiltration or encryption-based attacks leveraging outdated cryptographic techniques.

YARA Rule

rule DCP_DES_EncryptECB {
	meta:
		author = "_pusher_"
		description = "Look for DCP Des EncryptECB"
		date = "2016-02"
	strings:
		$c0 = { 53 80 78 ?? 00 75 16 B9 ?? ?? ?? 00 B2 01 A1 ?? ?? ?? 00 E8 ?? ?? ?? FF E8 ?? ?? ?? FF 8D 58 ?? 53 E8 ?? ?? FF FF 5B C3 }
	condition:
		any of them
}

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

• Scenario: Scheduled System Backup Using Veeam Backup & Replication
  Description: A legitimate backup process may invoke encryption routines as part of data compression or secure storage.
  Filter/Exclusion: Check for process parent or command line containing veeam or backup in the command line.

• Scenario: Windows Server Backup Using Windows Server Backup Tool
  Description: The built-in Windows Server Backup utility may use encryption during backup operations.
  Filter/Exclusion: Filter by process name wbadmin or check for presence of wbadmin in the command line.

• Scenario: Database Encryption Task Using Microsoft SQL Server
  Description: SQL Server may perform encryption operations during maintenance tasks or data encryption setup.
  Filter/Exclusion: Filter by process name sqlservr.exe or check for sqlcmd or sqlbackup in the command line.

• Scenario: Log File Compression Using PowerShell or 7-Zip
  Description: Administrators may use PowerShell or 7-Zip to compress log files, which could involve encryption-like operations.
  Filter/Exclusion: Filter by process name powershell.exe or 7z.exe, or check for compress or 7z in the command line.

• Scenario: Scheduled Job for Data Masking Using Talend or Informatica
  Description: Data masking jobs may include encryption steps to anonymize data.
  Filter/Exclusion: Filter by process name talend or informatica, or check for masking or encrypt in the command line.