Detects c# red/black-team tools via typelibguid

Hunt Hypothesis

This rule identifies potential adversary activity by detecting C#-based red and blue team tools through their unique TypeLibGUID signatures within Azure Sentinel logs. Proactively hunting for these specific identifiers allows the SOC team to distinguish legitimate security tooling from malicious C# processes that may mimic known utilities to evade detection.

YARA Rule

rule HKTL_NET_GUID_Sharp_SMBExec {
    meta:
        description = "Detects c# red/black-team tools via typelibguid"
        reference = "https://github.com/checkymander/Sharp-SMBExec"
        author = "Arnim Rupp"
        date = "2020-12-28"
    strings:
        $typelibguid0 = "344ee55a-4e32-46f2-a003-69ad52b55945" ascii nocase wide
    condition:
        (uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550) and any 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

• https://github.com/checkymander/Sharp-SMBExec
• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the “Detects c# red/black-team tools via typelibguid” rule, including suggested filters and exclusions:

• Scenario: Automated CI/CD Pipeline Builds

  • Context: Enterprise build servers (e.g., Jenkins, Azure DevOps) frequently compile C# applications using msbuild.exe or dotnet.exe. During the compilation process, these tools instantiate .NET assemblies that register specific TypeLibGUIDs associated with build automation libraries.
  • Filter/Exclusion: Exclude processes running under the context of known CI/CD service accounts (e.g., NT SERVICE\Jenkins, AZDO-BUILD-SVC) or restrict detection to exclude parent processes named msbuild.exe and dotnet.exe.

• Scenario: Microsoft Endpoint Configuration Manager (SCCM) Deployments

  • Context: During scheduled software deployments, SCCM utilizes C#-based agents (ccmexec.exe, WUAHandler) that interact with the Windows Registry to manage application manifests. These interactions often trigger TypeLibGUID events identical to those used by security testing tools like Nmap or custom Red Team injectors.
  • Filter/Exclusion: Create an exclusion for the parent process path C:\Program Files (x86)\Microsoft Configuration Manager\ and exclude specific TypeLibGUIDs known to be part of the SCCM client suite.

• Scenario: Enterprise Backup Solutions (e.g., Veeam, Commvault)

  • Context: Modern backup agents written in .NET often perform pre-backup validation or inventory scans. These agents load C# libraries that register TypeLibGUIDs to interface with the OS file system, mimicking the behavior of Black Team reconnaissance tools like BloodHound or SharpUp.
  • Filter/Exclusion: Exclude processes where the `