yzpack112UsAr

Hunt Hypothesis

This YARA rule targets specific binary patterns or code structures that may indicate the presence of a low-severity, potentially obfuscated, or legacy software component within the environment. Proactively hunting for these signatures helps the SOC team identify unusual or dormant artifacts that could serve as footholds for lateral movement or persistence, ensuring that low-fidelity indicators are not overlooked in the Azure Sentinel telemetry.

YARA Rule

rule yzpack112UsAr
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 5A 52 45 60 83 EC 18 8B EC 8B FC 33 C0 64 8B 40 30 78 0C 8B 40 0C 8B 70 1C AD 8B 40 08 EB 09 8B 40 34 83 C0 7C 8B 40 3C AB E9 [4] B4 09 BA 00 00 1F CD 21 B8 01 4C CD 21 40 00 00 00 50 45 00 00 4C 01 02 00 [4] 00 00 00 00 00 00 00 00 E0 00 [2] 0B 01 [4] 00 00 }

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 the yzpack utility (or a custom internal tool named yzpack112UsAr) to compress and archive log files or configuration backups before transferring them to an off-site backup server via rsync or Azure Blob Storage.
  • Filter/Exclusion: Exclude processes where the parent process is rsync, scp, az, or kubectl, and the file path contains /backups/, /logs/, or /tmp/ with a .tar.gz or .zip extension.
• Scenario: An automated Windows Task Scheduler job runs a custom PowerShell script that invokes yzpack112UsAr.exe to package application state data for a nightly integrity check, triggered by the Task Scheduler service (svchost.exe or taskschd.exe).
  • Filter/Exclusion: Exclude executions where the parent process is taskschd.exe or svchost.exe and the command line contains keywords like integrity, backup, or snapshot.
• Scenario: A CI/CD pipeline agent (e.g., Jenkins, GitLab Runner, or Azure DevOps Agent) executes a build step that uses yzpack112UsAr to bundle build artifacts for deployment, running under the jenkins.exe, gitlab-runner.exe, or vsts-agent.exe process.
  • Filter/Exclusion: Exclude processes where the parent process matches known CI/CD agent binaries (jenkins.exe, gitlab-runner.exe, vsts-agent.exe, docker.exe) and the working directory is within the agent’s workspace (e.g., /workspace/, /agent/, or C:\agent\).
• Scenario: A security team performs a **