VxNovember17768

Hunt Hypothesis

This rule detects the presence of a specific VxNovember malware variant, which adversaries may deploy to establish a foothold or execute malicious payloads within Azure environments. Proactively hunting for this signature allows the SOC team to identify low-severity intrusions early, preventing potential lateral movement or data exfiltration before the threat escalates.

YARA Rule

rule VxNovember17768
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 [2] 5E 81 EE [2] 50 33 C0 8E D8 80 3E [3] 0E 1F [2] FC }

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 legitimate enterprise backup solution (e.g., Veeam Backup & Replication or Commvault) creates temporary shadow copy files or staging areas that match the byte-pattern or structural heuristic of the VxNovember17768 signature during a full backup cycle.

  • Filter/Exclusion: Exclude processes originating from the backup service executable (e.g., vbrservice.exe, commvault\sim\sim.exe) or file paths within the designated backup repository directories (e.g., C:\Veeam\Backup\, D:\Commvault\Sim\).

• Scenario: A standard Windows scheduled task (Task Scheduler) runs a PowerShell script to perform routine log rotation or disk cleanup, where the script binary or its temporary execution context matches the YARA rule’s pattern for script-based execution or specific API calls.

  • Filter/Exclusion: Exclude events where the parent process is schtasks.exe or taskschd.msc, and the command line contains standard administrative verbs like Delete, Rotate, or Clean with known script paths (e.g., C:\Scripts\Maintenance\cleanup.ps1).

• Scenario: An IT management agent (e.g., Microsoft Endpoint Configuration Manager, SCCM, or Intune) deploys a new application or updates a system driver, creating a temporary .cab or .msi file in the %TEMP% or %SystemRoot%\Temp directory that triggers the file-based detection.

  • Filter/Exclusion: Exclude file creation events where the parent process is ccmexec.exe (SCCM) or intunemgmt.exe (Intune) and the file extension is .cab, .msi, or .tmp located in standard temp directories.

• Scenario: A developer or sysadmin uses a legitimate code analysis or