EPWv130

Hunt Hypothesis

This rule detects the presence of the EPWv130 YARA signature, which typically identifies specific malware families or malicious scripts that may be used for initial access or persistence. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to identify compromised endpoints or stored artifacts before they are actively executed or leveraged for lateral movement.

YARA Rule

rule EPWv130
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 06 57 1E 56 55 52 51 53 50 2E 8C 06 08 00 8C C0 83 C0 10 2E }

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 runs a local build script or CI/CD pipeline agent (e.g., Jenkins, GitLab Runner, or Azure DevOps Agent) that compiles C/C++ code or processes binary assets. The YARA rule EPWv130 may match specific compiler artifacts, linker outputs, or embedded version strings within the build cache or temporary directories.

  • Filter/Exclusion: Exclude processes originating from known build tool executables (e.g., msbuild.exe, dotnet.exe, java.exe, node.exe) or files located in standard build/cache directories (e.g., %TEMP%, C:\ProgramData\Jenkins, ~/.cache) when the parent process is a recognized build orchestrator.

• Scenario: An enterprise endpoint protection or backup solution (e.g., Veeam, Commvault, or Carbon Black) performs a full-file scan or restores a backup image. During the restore or scan process, the agent reads large binary files (like .vbk, .b2b, or .zip archives) into memory or temp space, potentially triggering the YARA signature if it matches common binary headers or embedded metadata.

  • Filter/Exclusion: Exclude events where the file path resides in backup-specific directories (e.g., C:\VeeamBackup, C:\Commvault\Backup) or where the parent process is a known backup agent executable (e.g., vbragent.exe, cvbackup.exe).

• Scenario: A system administrator performs a manual patch deployment or software installation using a package manager or installer (e.g., winget, choco, or msiexec.exe). The installer extracts temporary files or creates registry keys that match the YARA pattern, especially if the rule targets specific version strings, GUIDs, or DLL signatures common in commercial software