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_v2 {
   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:
      $BUILD_USER32 = {75 73 65 72 ?? ?? ?? 33 32 2E 64}
      $BUILD_ADVAPI32 = {61 64 76 61 ?? ?? ?? 70 69 33 32}
      $CONSTANT = {26 80 AC C8}
   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 3 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Scheduled System Maintenance Task
Description: A legitimate system maintenance task, such as schtasks.exe running a cleanup or update job, may trigger the rule due to similar command-line patterns.
Filter/Exclusion: Check for schtasks.exe with known maintenance job names (e.g., CleanupTask, WindowsUpdate) and exclude based on command-line arguments or process parent.
Scenario: PowerShell Script for Configuration Management
Description: A PowerShell script used by IT administrators for configuration management (e.g., Invoke-Command, Set-ItemProperty) may resemble malicious activity due to similar string patterns.
Filter/Exclusion: Filter out PowerShell scripts executed from known configuration management tools (e.g., Powershell.exe with -File parameter pointing to a known admin script path).
Scenario: Antivirus or EDR Tool Scanning Activity
Description: Antivirus or EDR tools (e.g., Windows Defender, CrowdStrike Falcon) may perform scanning activities that match the rule’s detection logic.
Filter/Exclusion: Exclude processes associated with known security tools (e.g., MsMpEng.exe, FalconService.exe) or filter based on process names and command-line arguments.
Scenario: Admin Task for Log Collection or Monitoring
Description: A legitimate admin task, such as using logman.exe or eventcreate.exe, may trigger the rule due to similar command-line structures.
Filter/Exclusion: Exclude processes related to log collection or monitoring tools (e.g., logman.exe, eventcreate.exe) or filter based on command-line parameters and process parent.
Scenario: Software Deployment via Group Policy or SCCM
Description: Software deployment tasks using Group Policy or SCCM (e.g., msiexec.exe,