BlackEnergyDDoSBotCrypter

Hunt Hypothesis

This rule identifies the presence of the BlackEnergy DDoS bot crypter, a component used by adversaries to encrypt and obfuscate botnet payloads for distributed denial-of-service attacks. Proactively hunting for this artifact allows the SOC to detect early-stage botnet infrastructure or dormant malware components before they are activated to launch volumetric attacks against Azure resources.

YARA Rule

rule BlackEnergyDDoSBotCrypter
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 [2] 81 EC 1C 01 00 00 53 56 57 6A 04 BE 00 30 00 00 56 FF 35 00 20 11 13 6A 00 E8 ?? 03 00 00 [2] 83 C4 10 ?? FF 89 7D F4 0F }

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

• Scenario: A legacy .NET application or internal tool uses a custom encryption/decryption library (e.g., BouncyCastle or a proprietary XOR-based obfuscation routine) that shares byte patterns with the BlackEnergy crypter. This often occurs in older financial reporting tools or internal dashboards that process encrypted data blobs in memory.
  • Filter/Exclusion: Exclude processes where the parent process is a known .NET host (e.g., dotnet.exe, w3wp.exe, iisexpress.exe) and the module path resides in a trusted application directory (e.g., C:\Program Files\InternalTools\).
• Scenario: A security team or developer performs manual testing of the YARA rule using a known-good sample or a test harness that intentionally loads the crypter logic to verify detection fidelity. This is common during quarterly threat hunting exercises or rule tuning sessions.
  • Filter/Exclusion: Exclude events where the user account is part of the SecurityTeam or DevOps AD group, or where the process command line contains specific test markers (e.g., --yara-test, --validation).
• Scenario: A third-party anti-malware or EDR agent (e.g., CrowdStrike Falcon, Carbon Black) performs its own heuristic scanning or memory inspection, potentially loading crypter-like structures into its own process space or spawning a helper process that mimics the crypter’s behavior during a deep scan.
  • Filter/Exclusion: Exclude processes where the parent process name matches known EDR/AV service executables (e.g., FalconSensor.exe, CbService.exe, MsMpEng.exe) and the process is running with SYSTEM or LocalService privileges.
• Scenario: A scheduled PowerShell script used for data archival or backup encryption uses a .NET assembly that includes a generic