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 detect and mitigate advanced persistent threats before they cause significant damage.

YARA Rule

rule IMPLANT_4_v13 {
   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:
      $XMLDOM1 = {81 BF 33 29 36 7B D2 11 B2 0E 00 C0 4F 98 3E 60}
      $XMLDOM2 = {90 BF 33 29 36 7B D2 11 B2 0E 00 C0 4F 98 3E 60}
      $XMLPARSE = {8B 06 [0-2] 8D 55 ?C 52 FF 75 08 [0-2] 50 FF 91 04 01 00 00
         66 83 7D ?C FF 75 3? 8B 06 [0-2] 8D 55 F? 52 50 [0-2] FF 51 30 85 C0
         78 2?}
      $EXP1 = "DispatchCommand"
      $EXP2 = "DispatchEvent"
      $BDATA = {85 C0 74 1? 0F B7 4? 06 83 C? 28 [0-6] 72 ?? 33 C0 5F 5E 5B 5D
         C2 08 00 8B 4? 0? 8B 4? 0? 89 01 8B 4? 0C 03 [0-2] EB E?}
   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 6 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Scheduled System Maintenance Task
Description: A legitimate scheduled task runs a script that mimics the behavior of the BlackEnergy/Voodoo Bear implant, such as downloading or executing files from internal repositories.
Filter/Exclusion: Check for task_name containing “maintenance” or “sysupdate” and ensure the script path is within a known internal maintenance directory (e.g., C:\Windows\System32\Tasks\).
Scenario: Admin User Performing Remote Desktop Session
Description: An admin user is performing a remote desktop session and the system logs show suspicious process creation or network activity that resembles the implant’s behavior.
Filter/Exclusion: Filter by user_name containing “admin” or “svc” and check for process_parent matching the RDP session process (e.g., tsclient.exe, mstsc.exe).
Scenario: Antivirus or Endpoint Protection Scan
Description: A legitimate antivirus or endpoint protection tool is performing a full system scan and temporarily creates or modifies files that match the implant’s file signatures.
Filter/Exclusion: Filter by process_name containing “avast.exe”, “bitdefender.exe”, or “mcafee.exe” and check for file_path in known security software directories.
Scenario: Software Update Deployment via SCCM
Description: A Software Center or SCCM (System Center Configuration Manager) update deployment is triggering file downloads or registry changes that resemble the implant’s activity.
Filter/Exclusion: Filter by process_name containing “ccmexec.exe” or “setup.exe” and check for file_path in SCCM deployment directories (e.g., C:\Windows\CCM\).
Scenario: Legitimate PowerShell Script for Log Collection
Description: A PowerShell script used for log collection or