Detects .NET red/black-team tools via name

Hunt Hypothesis

This rule identifies the execution of known .NET-based Red and Black team utility names to distinguish legitimate security testing activities from potential adversary reconnaissance or tool deployment. Proactive hunting for these signals in Azure Sentinel is essential to validate authorized operations and rapidly detect unauthorized use of similar frameworks by threat actors attempting to blend into normal administrative traffic.

YARA Rule

rule HKTL_NET_NAME_SharpBuster {
    meta:
        description = "Detects .NET red/black-team tools via name"
        reference = "https://github.com/passthehashbrowns/SharpBuster"
        author = "Arnim Rupp"
        date = "2021-01-22"
    strings:
        $name = "SharpBuster" ascii wide
        $compile = "AssemblyTitle" ascii wide
    condition:
        (uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550) and all 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 2 string patterns in its detection logic.

References

• https://github.com/passthehashbrowns/SharpBuster
• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the rule “Detects .NET red/blue-team tools via name,” along with suggested filters or exclusions:

• Scenario: Automated Backup and Archiving Jobs

  • Context: Enterprise backup solutions like Veeam Backup & Replication or Rubrik often utilize underlying .NET executables (e.g., Veeam.Backup.Service.exe, Rubrik.Cli.exe) that run on a schedule to perform data snapshots. These processes frequently match the naming patterns of security tools due to their heavy reliance on the .NET framework for management interfaces.
  • Filter/Exclusion: Exclude specific service executable names known to be part of the backup infrastructure from the detection logic, or filter out alerts where the parent process is a recognized scheduler (e.g., Task Scheduler or System) running during defined maintenance windows.

• Scenario: Internal DevOps and CI/CD Pipeline Execution

  • Context: Continuous Integration servers like Jenkins, GitLab Runner, or internal build agents often execute .NET-based automation scripts (e.g., BuildAgent.exe, AzurePipelinesAgent.exe) to compile code, run unit tests, or deploy applications. These tools mimic the behavior of red-team reconnaissance tools by scanning file systems and executing commands.
  • Filter/Exclusion: Create a whitelist for known CI/CD agent processes running on dedicated build servers (identified by hostname regex) and exclude alerts where the process path resides within the specific DevOps directory structure (e.g., C:\Program Files\Jenkins\).

• Scenario: Endpoint Management and Patching Agents

  • Context: Unified Endpoint Management platforms such as Microsoft Intune, SCCM (Configuration Manager), or Jamf utilize .NET agents to push updates, inventory hardware, and manage software compliance.