AHTeamEPProtector03fakeMicrosoftVisualC70FEUERRADER

Hunt Hypothesis

This detection targets adversaries employing a fake Microsoft Visual C++ installer to masquerade as legitimate software while executing malicious payloads on endpoints. A proactive hunt is essential in Azure Sentinel to identify early-stage supply chain compromises or initial access attempts that may evade standard signature-based defenses due to the rule’s low severity classification.

YARA Rule

rule AHTeamEPProtector03fakeMicrosoftVisualC70FEUERRADER
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 90 [46] 90 FF E0 6A 00 68 [4] E8 [4] BF [4] 8B C7 E8 [4] 89 65 00 8B F4 89 3E 56 FF 15 [4] 8B 4E ?? 89 0D [3] 00 8B 46 00 A3 }

condition:
		$a0 at pe.entry_point
}

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.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the AHTeamEPProtector03fakeMicrosoftVisualC70FEUERRADER rule, which detects processes masquerading as Microsoft Visual C++ Redistributable components (often associated with vcredist, msvcp, or similar binaries) that exhibit suspicious behavior:

• Scenario 1: Automated Patch Deployment via SCCM/Intune

  • Context: The enterprise uses Microsoft Endpoint Configuration Manager (SCCM) or Intune to push the latest Visual C++ Redistributable updates (vc_redist.x64.exe) during a scheduled maintenance window. The installer often spawns child processes that mimic the signature of the official redistributable but may be flagged if the parent process chain is complex or if the installation occurs on a non-standard port.
  • Suggested Filter/Exclusion: Create an exclusion for the specific executable hash of vc_redist.x64.exe (or .x86) located in the standard deployment source path (e.g., C:\Windows\CCM\Logs or C:\ProgramData\Microsoft\MSCCM). Additionally, filter alerts where the parent process is ccmsetup.exe or msiexec.exe.

• Scenario 2: Legacy Application Installation on Build Servers

  • Context: On build servers (e.g., Jenkins agents or Azure DevOps runners), legacy .NET applications require specific versions of Visual C++ libraries. During the CI/CD pipeline, a scheduled job installs these dependencies using a custom wrapper script that launches vcredist.exe. The YARA rule may flag this if the wrapper script is not recognized as a trusted parent, causing the “fake” detection logic to trigger on legitimate library installation.
  • Suggested Filter/Exclusion: Exclude alerts originating from specific build server hostnames (e.g., `BUILD