DevCv4

Hunt Hypothesis

This rule detects the presence of specific development or custom code artifacts, potentially indicating an adversary has deployed custom tooling or established a foothold within the environment. Proactively hunting for these signatures allows the SOC team to identify low-and-slow persistence mechanisms or initial access vectors that may evade standard behavioral detections in Azure Sentinel.

YARA Rule

rule DevCv4
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 89 E5 83 EC 08 83 C4 F4 6A ?? A1 [3] 00 FF D0 E8 ?? FF FF FF }

condition:
		$a0
}

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

• Scenario: A developer or DevOps engineer runs a local build pipeline or CI/CD agent (e.g., Jenkins, GitLab Runner, or Azure DevOps Agent) on a build server or developer workstation. The YARA rule DevCv4 likely matches the binary or script artifacts generated by the build process (such as compiled executables, temporary JAR/WAR files, or Node.js node_modules binaries) that reside in standard build directories.

  • Filter/Exclusion: Exclude processes or file paths where the parent process is a known CI/CD agent (e.g., jenkins.exe, gitlab-runner.exe, agent.exe) or where the file path contains standard build directories like \build\, \target\, \dist\, or \node_modules\.

• Scenario: An IT administrator performs a scheduled software deployment or patching task using a tool like SCCM (System Center Configuration Manager) or PDQ Deploy. The deployment agent writes installer packages or temporary executables to disk, which may match the DevCv4 signature if the rule targets common development or utility binaries (e.g., 7z.exe, unzip.exe, or specific compiler binaries) used during the extraction or installation phase.

  • Filter/Exclusion: Exclude events where the process name is a known deployment agent (e.g., ccmsetup.exe, pdqdeploy.exe, wsus.exe) or where the file path is located in temporary deployment directories such as \C:\Windows\CCMSetup\ or \C:\Temp\PDQ\.

• Scenario: A data scientist or ML engineer runs a Jupyter Notebook or Python script that invokes a native C/C++ extension or a compiled Python package (e.g., numpy, pandas, or scipy shared libraries). The YARA rule may match the `.