VxVirusConstructorIVPbased

Hunt Hypothesis

This detection identifies the presence of a specific virus constructor utilizing IVP-based mechanisms, which often indicates an adversary attempting to establish persistence or deploy custom malware within the environment. A proactive hunt is essential in Azure Sentinel to uncover early-stage infections that may evade traditional signature-based defenses and prevent potential lateral movement before they escalate into critical incidents.

YARA Rule

rule VxVirusConstructorIVPbased
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E9 [2] E8 [2] 5D [5] 81 ED [6] E8 [2] 81 FC [4] 8D [3] BF [2] 57 A4 A5 }

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 VxVirusConstructorIVPbased detection rule, including suggested filters and exclusions:

• Antivirus Engine Self-Update Scans

  • Scenario: The enterprise endpoint protection suite (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, or Symantec Endpoint Protection) performs a scheduled daily update. During this process, the antivirus engine downloads and extracts new definition packs, which often involve constructing temporary memory structures that mimic IVP-based virus constructor signatures.
  • Filter/Exclusion: Exclude processes matching C:\Program Files\CrowdStrike\FalconSensor\csfalcon.exe (or equivalent vendor executables) when the parent process is a scheduled task service (svchost.exe with specific service names like wuauserv). Alternatively, whitelist file paths containing \Definitions\ or \Updates\.

• Software Deployment via SCCM/Intune

  • Scenario: The IT operations team deploys a new application package using Microsoft Endpoint Configuration Manager (SCCM) or Microsoft Intune. The deployment agent extracts compressed payloads and constructs temporary installation directories, triggering the YARA rule due to the creation of IVP-like structures during the unpacking phase.
  • Filter/Exclusion: Create an exclusion based on the parent process ccmsetup.exe (SCCM) or Microsoft.IntuneManagementAgent. Additionally, filter out events occurring within specific deployment windows (e.g., 02:00–04:00 UTC) where mass deployments are known to occur.

• Backup and Archiving Operations

  • Scenario: Enterprise backup solutions like Veeam Backup & Replication or Commvault run nightly jobs that compress and archive large datasets. The constructor logic used by these tools to generate incremental backups