yCv13byAshkbizDanehkar

Hunt Hypothesis

This detection identifies potential file-based threats matching the specific signature of the “yCv13byAshkbizDanehkar” YARA rule, which may indicate early-stage malware or suspicious artifacts within the environment. Proactively hunting for this low-severity signal in Azure Sentinel allows the SOC team to validate false positives and uncover stealthy adversary activity that might otherwise be overlooked by automated alerting thresholds.

YARA Rule

rule yCv13byAshkbizDanehkar
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 81 EC C0 00 00 00 53 56 57 8D BD 40 FF FF FF B9 30 00 00 00 B8 CC CC CC CC F3 AB 60 E8 00 00 00 00 5D 81 ED 84 52 41 00 B9 75 5E 41 00 81 E9 DE 52 41 00 8B D5 81 C2 DE 52 41 00 8D 3A 8B F7 33 C0 EB 04 90 EB 01 C2 AC }

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

Here are 5 specific false positive scenarios for the detection rule yCv13byAshkbizDanehkar, along with targeted filters and exclusions suitable for an enterprise environment:

• Antivirus Engine Signature Updates

  • Scenario: The YARA rule triggers when the endpoint protection suite (e.g., CrowdStrike Falcon or Microsoft Defender for Endpoint) executes its scheduled signature update task. These updates often involve downloading and unpacking large binary archives that match the heuristic patterns defined in yCv13byAshkbizDanehkar.
  • Filter/Exclusion: Create a process exclusion for the specific antivirus service executable (e.g., C:\Program Files\CrowdStrike\FalconSensor\csfalcon.exe or MsMpEng.exe) and exclude file paths within the vendor’s installation directory (C:\ProgramData\Microsoft\Windows Defender\).

• Enterprise Backup Agent Operations

  • Scenario: During nightly backup windows, agents like Veeam Backup & Replication or Commvault scan and compress large datasets. The rule may misinterpret the high-volume file I/O and temporary staging files created by these agents as suspicious activity matching the YARA signature.
  • Filter/Exclusion: Exclude processes running under the backup service accounts (e.g., VeeamBRService or CommServe) and add a path exclusion for the backup staging directories (e.g., D:\BackupStaging\*).

• Software Deployment via Configuration Management

  • Scenario: When Microsoft SCCM (Configuration Manager) or Ansible pushes software updates to endpoints, it extracts installation packages (.msi/.cab) in the system temp folder. The extraction process generates file structures that align with the detection logic of `yCv13byAshkbizD