MSLRHv032afakeMSVC70DLLMethod3emadicius

Hunt Hypothesis

This rule detects the presence of a specific malicious DLL masquerading as a Microsoft Visual C++ 7.0 runtime component, a common technique used by adversaries to achieve persistence or code execution through trusted binary impersonation. Proactively hunting for this artifact in Azure Sentinel allows the SOC team to identify low-severity, file-based implants that may be hiding in plain sight within endpoint file systems before they are leveraged for further lateral movement or privilege escalation.

YARA Rule

rule MSLRHv032afakeMSVC70DLLMethod3emadicius
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 53 8B 5D 08 56 8B 75 0C 5E 5B 5D EB 05 E8 EB 04 40 00 EB FA E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 50 E8 02 00 00 00 29 5A 58 6B C0 03 E8 02 00 00 00 29 5A 83 C4 04 58 74 04 75 02 EB 02 EB 01 81 0F 31 50 0F 31 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF }

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

• Legacy .NET Framework 1.0/1.1 Application Deployment

  • Scenario: An IT administrator deploys a legacy line-of-business application (e.g., an old inventory management tool or a specialized CAD plugin) that was compiled using the original Microsoft Visual C++ 7.0 (VS2002) runtime. These applications often bundle or dynamically load msvcr70.dll or rely on specific PE header structures that mimic the “fake” MSVC 7.0 signature detected by the YARA rule, especially if the binary is slightly modified or repacked by a deployment tool like SCCM or Intune.
  • Filter/Exclusion: Exclude files located in specific legacy application directories (e.g., C:\Program Files\LegacyApp\bin\) or exclude processes where the parent is a known deployment agent (e.g., CCMSetup.exe, IntuneAgent.exe) and the file path matches *msvcr70.dll or *msvcr70d.dll.

• Visual Studio 2002/2003 Development Environment

  • Scenario: A developer is working on a legacy C++ project using Visual Studio 2002 or 2003. The IDE loads the native msvcr70.dll runtime library into memory for debugging or execution. The YARA rule may flag the DLL itself or the debug helper processes (msvcmrt.dll or similar) if they exhibit the specific PE structure anomalies targeted by “Method3emadicius,” particularly if the developer has applied custom patches or if the DLL is loaded from a non-standard path during a build process.
  • Filter/Exclusion: Exclude files with the name msvcr70.dll or msvcr70d.dll when the parent process is