DevC4992BloodshedSoftware

Hunt Hypothesis

This rule identifies the presence of Bloodshed Software development tools, which adversaries may utilize to compile custom malware or exploit code directly on compromised hosts. Proactively hunting for these artifacts helps the SOC team detect early-stage development or staging activities that often precede more complex post-exploitation actions in the Azure environment.

YARA Rule

rule DevC4992BloodshedSoftware
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 89 E5 83 EC 08 C7 04 24 01 00 00 00 FF 15 [3] 00 E8 C8 FE FF FF 90 8D B4 26 00 00 00 00 55 89 E5 83 EC 08 C7 04 24 02 00 00 00 FF 15 [3] 00 E8 A8 FE FF FF 90 8D B4 26 00 00 00 00 55 8B 0D [3] 00 89 E5 5D FF E1 8D 74 26 00 55 8B 0D }

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 Development Tooling: The rule likely targets specific memory patterns or binary signatures associated with older versions of Microsoft Visual Studio or JetBrains Rider that use the .NET Framework. Legitimate developers running these IDEs on build servers or developer workstations may trigger the rule if the YARA signature matches the IDE’s core libraries or debugging agents.

  • Filter/Exclusion: Exclude processes where the parent executable is devenv.exe (Visual Studio) or rider64.exe/rider.exe (JetBrains Rider), or exclude files located in standard installation paths like C:\Program Files\Microsoft Visual Studio\ or C:\Program Files\JetBrains\.

• Scheduled Build Agents (Jenkins/GitLab CI): In enterprise CI/CD pipelines, build agents often run Jenkins (jenkins.exe) or GitLab Runner (gitlab-runner.exe) which spawn child processes for compilation tasks. If the YARA rule matches the memory footprint of the MSBuild (MSBuild.exe) or CSC (C# Compiler) processes during heavy compilation cycles, it can trigger false positives on build nodes.

  • Filter/Exclusion: Exclude processes where the parent chain includes jenkins.exe, gitlab-runner.exe, or agent.exe (Azure DevOps), or exclude processes running from standard build agent directories like C:\jenkins\ or C:\GitLab\runner\.

• Database Maintenance Scripts (SQL Server): The rule name “Bloodshed” might imply a reference to specific memory corruption patterns or legacy C++ libraries. SQL Server (sqlservr.exe) often loads native C++ extensions or uses ODBC drivers that share similar memory layouts. Scheduled maintenance jobs (e.g., sp_spaceused or index rebuilds) executed