BlackEnergy / Voodoo Bear Implant by APT28

Hunt Hypothesis

The hypothesis is that the detection identifies potential BlackEnergy / Voodoo Bear implant activity by APT28, characterized by suspicious file execution and network communication patterns indicative of command and control. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate advanced persistent threats before they cause significant damage.

YARA Rule

rule IMPLANT_4_v6 {
   meta:
      description = "BlackEnergy / Voodoo Bear Implant by APT28"
      author = "US CERT"
      reference = "https://www.us-cert.gov/ncas/current-activity/2017/02/10/Enhanced-Analysis-GRIZZLY-STEPPE"
      date = "2017-02-10"
      score = 85
   strings:
      $STR1 = "DispatchCommand" wide ascii
      $STR2 = "DispatchEvent" wide ascii
   condition:
      (uint16(0) == 0x5A4D or uint16(0) == 0xCFD0 or uint16(0) == 0xC3D4 or
      uint32(0) == 0x46445025 or uint32(1) == 0x6674725C) and all 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 2 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Scheduled System Maintenance Task
Description: A legitimate system maintenance task (e.g., schtasks.exe) is executed to update or clean system files.
Filter/Exclusion: Exclude processes initiated by the schtasks.exe with a known legitimate task name, such as UpdateSystemFiles or CleanupTemp.
Scenario: Admin User Performing Remote Desktop Session
Description: An admin user is performing a remote desktop session (mstsc.exe) and is executing commands that match the rule’s signature.
Filter/Exclusion: Exclude processes launched from the mstsc.exe command line with a known admin user context or from a trusted IP address range.
Scenario: PowerShell Script for Patch Management
Description: A PowerShell script (powershell.exe) is used to apply patches or configure system settings, which may trigger the rule due to similar command patterns.
Filter/Exclusion: Exclude processes where the command line includes -File and the script path is within a known patch management directory (e.g., C:\PatchManagement\).
Scenario: Logon Session Initialization by Local Admin
Description: A local administrator logs in and initializes a session, which may involve processes that resemble the malicious behavior.
Filter/Exclusion: Exclude processes initiated by the Local System or Administrator account during logon events with a known session initialization pattern.
Scenario: Antivirus or EDR Tool Performing Scan
Description: A legitimate antivirus or EDR tool (e.g., Microsoft Defender, CrowdStrike Falcon) is performing a system scan, which may include similar process creation patterns.
Filter/Exclusion: Exclude processes with the parent process being the antivirus/EDR service or with a known scan command line argument (e.g., --full-scan).