BlackEnergy / Voodoo Bear Implant by APT28

Hunt Hypothesis

The hypothesis is that the detection rule 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 threat activity early in the attack lifecycle.

YARA Rule

rule IMPLANT_4_v7 {
   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:
      $sb1 = {C7 [1-5] 33 32 2E 64 C7 [1-5] 77 73 32 5F 66 C7 [1-5] 6C 6C}
      $sb2 = {C7 [1-5] 75 73 65 72 C7 [1-5] 33 32 2E 64 66 C7 [1-5] 6C 6C}
      $sb3 = {C7 [1-5] 61 64 76 61 C7 [1-5] 70 69 33 32 C7 [1-5] 2E 64 6C 6C}
      $sb4 = {C7 [1-5] 77 69 6E 69 C7 [1-5] 6E 65 74 2E C7 [1-5] 64 6C 6C}
      $sb5 = {C7 [1-5] 73 68 65 6C C7 [1-5] 6C 33 32 2E C7 [1-5] 64 6C 6C}
      $sb6 = {C7 [1-5] 70 73 61 70 C7 [1-5] 69 2E 64 6C 66 C7 [1-5] 6C}
      $sb7 = {C7 [1-5] 6E 65 74 61 C7 [1-5] 70 69 33 32 C7 [1-5] 2E 64 6C 6C}
      $sb8 = {C7 [1-5] 76 65 72 73 C7 [1-5] 69 6F 6E 2E C7 [1-5] 64 6C 6C}
      $sb9 = {C7 [1-5] 6F 6C 65 61 C7 [1-5] 75 74 33 32 C7 [1-5] 2E 64 6C 6C}
      $sb10 = {C7 [1-5] 69 6D 61 67 C7 [1-5] 65 68 6C 70 C7 [1-5] 2E 64 6C 6C}
   condition:
      (uint16(0) == 0x5A4D or uint16(0) == 0xCFD0 or uint16(0) == 0xC3D4 or
      uint32(0) == 0x46445025 or uint32(1) == 0x6674725C) and 3 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 10 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 copying files or modifying registry keys.
Filter/Exclusion: Exclude tasks associated with known system maintenance tools (e.g., schtasks.exe, Task Scheduler), or filter by process name and command-line arguments matching known maintenance scripts.
Scenario: Admin User Performing File Integrity Check
Description: An admin user is using a tool like Tripwire or OSSEC to check for file integrity, which may involve copying or modifying files in a manner similar to the implant.
Filter/Exclusion: Exclude processes initiated by admin users with known security tools, or filter by user context and tool-specific command-line arguments.
Scenario: PowerShell Script for Log Collection
Description: A legitimate PowerShell script used for log collection or system monitoring (e.g., Get-EventLog, Export-EventLog) may trigger the rule due to file operations or registry modifications.
Filter/Exclusion: Exclude PowerShell scripts that match known log collection tools or are executed by authorized monitoring tools (e.g., PowerShell.exe with Export-EventLog).
Scenario: Antivirus Quarantine Process
Description: An antivirus tool (e.g., Kaspersky, Bitdefender) may quarantine a file that matches the implant’s signature, causing the rule to trigger.
Filter/Exclusion: Exclude processes related to antivirus tools (e.g., kavsvc.exe, bdagent.exe) or filter by file paths commonly used by antivirus quarantine mechanisms.
Scenario: Database Backup Job
Description: A database backup job (e.g., using SQL Server Backup, mysqldump) may involve copying files or interacting with the