HACKSTOPv110v111

Hunt Hypothesis

This detection identifies potential malicious activity flagged by the HACKSTOPv110v111 YARA signature, which may indicate early-stage threats or specific file-based anomalies within the environment. Proactively hunting for this signal in Azure Sentinel allows the SOC team to validate low-severity alerts before they escalate, ensuring that subtle indicators of compromise are not overlooked during routine monitoring.

YARA Rule

rule HACKSTOPv110v111
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B4 30 CD 21 86 E0 3D [2] 73 ?? B4 2F CD 21 B0 ?? B4 4C CD 21 50 B8 [2] 58 EB }

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

Here are 4 specific false positive scenarios for the HACKSTOPv110v111 YARA rule detection logic, including suggested filters and exclusions:

• Scenario: Scheduled Antivirus Definition Updates

  • Context: The enterprise endpoint protection suite (e.g., CrowdStrike Falcon or Microsoft Defender for Endpoint) performs a daily automated definition update at 02:00 AM. This process often involves unpacking compressed signature databases and executing temporary scripts that match the YARA signatures in HACKSTOPv110v111.
  • Suggested Filter/Exclusion: Exclude processes where the parent executable is falcon.sys (CrowdStrike) or MsMpEng.exe (Defender), specifically when running on the scheduled task path \Microsoft\Windows\Windows Defender\MpCmdRun. Alternatively, add a time-based filter to suppress alerts between 01:30 and 02:45 daily.

• Scenario: Software Deployment via Configuration Management

  • Context: During business hours, the IT Operations team uses Microsoft Endpoint Configuration Manager (MECM/SCCM) or Ansible Tower to push new application patches to a group of workstations. The deployment agent extracts installation packages and executes a temporary installer binary that triggers the rule due to its file structure resembling the threat pattern.
  • Suggested Filter/Exclusion: Create an exclusion for process names matching ccmsetup.exe (SCCM) or ansible-runner, provided the user context is a service account named DOMAIN\DeployService. Additionally, filter out events where the command line contains specific deployment flags like /quiet or --update-id.

• Scenario: Automated Backup and Archiving Jobs

  • Context: The nightly backup routine managed by **Veeam Backup & Rep