Inbuildv10hard

Hunt Hypothesis

This rule identifies the presence of the Inbuildv10hard YARA signature, which typically indicates a specific variant of in-memory malware or a hardcoded build artifact often used for initial access or persistence. Proactively hunting for this signature allows the SOC team to detect low-severity threats that may evade traditional behavioral detections, ensuring early identification of compromised hosts before they progress to lateral movement or data exfiltration.

YARA Rule

rule Inbuildv10hard
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B9 [2] BB [2] 2E [2] 2E [2] 43 E2 }

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

• Scenario: A developer or DevOps engineer uses a build automation tool like Jenkins or GitHub Actions to compile a C/C++ project that explicitly includes the #include <v10.h> header (or similar version-specific internal headers) as part of a legacy library integration. The YARA rule may match the binary or source file if it scans build artifacts or temporary compilation directories.

  • Filter/Exclusion: Exclude files located in standard build output directories (e.g., */build/*, */dist/*, */target/*) or exclude processes spawned by known CI/CD agents (e.g., jenkins-slave.exe, agent.exe from GitHub Actions) when the file path contains v10 or matches the specific header name.

• Scenario: An IT administrator runs a scheduled PowerShell script or batch job to patch or update a specific version of a third-party SDK (e.g., Visual Studio Build Tools or Node.js global packages) where the installation path or package name includes “v10” (e.g., node_modules/v10-hard, sdk/v10). The rule might trigger on the file system event or the process command line if it inspects arguments or file names.

  • Filter/Exclusion: Exclude file paths that match known SDK or package manager directories (e.g., */node_modules/*, */.nuget/packages/*, */VisualStudio/SDKs/*) and exclude processes like powershell.exe or cmd.exe if the command line contains install, update, or restore alongside the “v10” string.

• Scenario: A security team or QA engineer runs a regression test suite using a tool like Selenium or Cypress that loads a test fixture or mock server binary named `inbuild_v10