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_v11 {
   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:
      $ = "/c format %c: /Y /X /FS:NTFS"
      $ = ".exe.sys.drv.doc.docx.xls.xlsx.mdb.ppt.pptx.xml.jpg.jpeg.ini.inf.ttf" wide
      $ = ".dll.exe.xml.ttf.nfo.fon.ini.cfg.boot.jar" wide
      $= ".crt.bin.exe.db.dbf.pdf.djvu.doc.docx.xls.xlsx.jar.ppt.pptx.tib.vhd.iso.lib.mdb.accdb.sql.mdf.xml.rtf.ini.cf g.boot.txt.rar.msi.zip.jpg.bmp.jpeg.tiff" wide
      $tempfilename = "%ls_%ls_%ls_%d.~tmp" ascii wide
   condition:
      (uint16(0) == 0x5A4D or uint16(0) == 0xCFD0 or uint16(0) == 0xC3D4 or
      uint32(0) == 0x46445025 or uint32(1) == 0x6674725C) and 2 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 1 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Legitimate scheduled backup job using wbadmin
Description: A scheduled Windows Backup Administrator task using wbadmin may trigger the rule due to similar command-line activity.
Filter/Exclusion: Check for wbadmin in the command line and exclude processes with wbadmin in the command line or associated with the Windows Backup service.
Scenario: System update or patching using wusa.exe
Description: Windows Update Standalone Setup (wusa.exe) may be flagged due to its use of similar command-line parameters or file names.
Filter/Exclusion: Exclude processes with wusa.exe or check for the presence of WindowsUpdate in the command line or process name.
Scenario: Admin task using PowerShell to manage services
Description: A legitimate administrative task using PowerShell to start/stop services (e.g., Start-Service, Stop-Service) may resemble malicious activity.
Filter/Exclusion: Filter out PowerShell scripts or commands that include Start-Service, Stop-Service, or are executed by a trusted admin account.
Scenario: Legitimate use of msiexec.exe for software deployment
Description: msiexec.exe is commonly used for installing software and may be mistaken for a malicious payload.
Filter/Exclusion: Exclude processes with msiexec.exe or check for the presence of .msi or .msp files in the command line.
Scenario: Use of certutil for certificate management
Description: certutil is often used for managing certificates and may be flagged due to its ability to execute scripts or download files.
Filter/Exclusion: Exclude processes with certutil or check for the presence of certificate-related commands like -addstore or `-