VxGrazie883

Hunt Hypothesis

This hunt hypothesis targets the specific malware signature identified by the VxGrazie883 YARA rule to detect early-stage file-based threats that may evade standard heuristic scans. Proactively hunting for this behavior in Azure Sentinel allows the SOC team to validate low-severity alerts against actual endpoint activity, ensuring that potential false positives are distinguished from genuine initial infection vectors before they escalate.

YARA Rule

rule VxGrazie883
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 1E 0E 1F 50 06 BF 70 03 B4 1A BA 70 03 CD 21 B4 47 B2 00 BE 32 04 CD 21 }

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 VxGrazie883 detection rule, including suggested filters and exclusions tailored for an enterprise environment:

• Scenario: Automated Patch Deployment via SCCM/Intune

  • Context: The System Center Configuration Manager (SCCM) or Microsoft Intune client executes a scheduled job to download and install critical security updates. During this process, the ccmsetup.exe or Microsoft.Update.Client service spawns temporary worker processes that match the VxGrazie883 signature due to embedded script interpreters.
  • Filter/Exclusion: Create an exclusion based on the parent process name (ccmsetup.exe, IntuneAgent.exe) and the file path prefix (e.g., C:\Program Files\Microsoft Configuration Manager\). Additionally, exclude alerts where the user context is SYSTEM or a specific service account like SVC-PATCHING.

• Scenario: Endpoint DLP Agent Scanning

  • Context: The Symantec Data Loss Prevention (DLP) agent performs real-time content inspection on large document repositories. When scanning archives containing embedded macros, the DLP engine (Symantec.DLP.Agent.exe) generates a temporary analysis process that triggers the VxGrazie883 rule due to its use of similar memory allocation patterns.
  • Filter/Exclusion: Apply a filter excluding alerts where the file hash matches known good hashes for the DLP agent’s analysis module. Alternatively, exclude the specific process Symantec.DLP.Agent.exe and its child processes when running in the context of the DLP-Service user account.

• Scenario: Scheduled PowerShell Compliance Reporting

  • Context: A nightly scheduled task runs a custom compliance script using powershell.exe to generate audit logs for regulatory requirements (e.g