Implant 7 by APT29

Hunt Hypothesis

The detection identifies potential Implant 7 activity by APT29, indicating the presence of a sophisticated, persistent malware used for long-term access and 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_7_v1 {
   meta:
      description = "Implant 7 by APT29"
      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 = { 8A 44 0A 03 32 C3 0F B6 C0 66 89 04 4E 41 3B CF 72 EE }
      $STR2 = { F3 0F 6F 04 08 66 0F EF C1 F3 0F 7F 04 11 83 C1 10 3B CF 72 EB }
   condition:
      (uint16(0) == 0x5A4D) and ($STR1 or $STR2)
}

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

• https://www.us-cert.gov/ncas/current-activity/2017/02/10/Enhanced-Analysis-GRIZZLY-STEPPE
• Source Rule

False Positive Guidance

• Scenario: Legitimate scheduled system maintenance task using schtasks.exe
  Filter/Exclusion: Check for schtasks.exe with Create or Modify actions and filter by known maintenance task names (e.g., Windows Update, Disk Defragmenter)

• Scenario: Administrative user performing a system cleanup using del or rmdir commands
  Filter/Exclusion: Exclude processes initiated by users with Administrators group membership and filter by known cleanup paths (e.g., C:\Windows\Temp, C:\Users\*\AppData\Local\Temp)

• Scenario: Use of PowerShell for legitimate configuration management (e.g., Invoke-Command, Set-ItemProperty)
  Filter/Exclusion: Filter out PowerShell scripts that match known configuration management tools (e.g., PSConfig, PSModule) or use Get-Command to identify known administrative cmdlets

• Scenario: Deployment of a legitimate third-party tool (e.g., 7-Zip, WinRAR) with command-line execution
  Filter/Exclusion: Exclude processes that match known legitimate compression tools and check for known command-line arguments used in normal operation

• Scenario: Use of PsExec for remote administration or patching tasks
  Filter/Exclusion: Filter out PsExec usage where the source is a trusted internal server and the destination is a known internal host within the enterprise network