VProtectorvcasm

Hunt Hypothesis

This detection identifies the execution of the VProtectorvcasm component, which may indicate legitimate virtualization protection activity or potential adversary attempts to leverage this module for stealthy persistence and code integrity verification within the Azure environment. A proactive hunt is recommended to distinguish between expected baseline behavior and anomalous usage patterns that could signal an attacker exploiting this trusted process to evade detection or establish a foothold on compromised hosts.

YARA Rule

rule VProtectorvcasm
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 00 00 00 00 4B 45 52 4E 45 4C 33 32 2E 64 6C 6C 00 00 55 53 45 52 33 32 2E 64 6C 6C 00 00 47 44 49 33 32 2E 64 6C 6C 00 00 00 00 00 00 00 00 47 65 74 50 72 6F 63 41 64 64 72 65 73 73 00 00 00 47 65 74 4D 6F 64 75 6C 65 48 61 6E 64 6C 65 41 00 00 00 4C 6F 61 64 4C 69 62 72 61 72 79 41 00 00 00 53 6C 65 65 70 00 00 00 47 65 74 56 65 72 73 69 6F 6E 00 00 00 47 65 74 43 6F 6D 6D 61 6E 64 4C 69 6E 65 41 00 00 00 47 65 74 53 74 61 72 74 75 70 49 6E 66 6F 41 00 00 00 47 65 74 41 43 50 00 00 00 43 72 65 61 74 65 54 68 72 65 61 64 00 00 00 44 65 66 57 69 6E 64 6F 77 50 72 6F 63 41 00 00 00 52 65 67 69 73 74 65 72 43 6C 61 73 73 45 78 41 00 00 00 43 72 65 61 74 65 57 69 6E 64 6F 77 45 78 41 00 00 00 47 65 74 53 79 73 74 65 6D 4D 65 74 72 69 63 73 00 00 00 53 68 6F 77 57 69 6E 64 6F 77 00 00 00 47 65 74 44 43 00 00 00 52 65 6C 65 61 73 65 44 43 00 00 00 46 69 6E 64 57 69 6E 64 6F 77 41 00 00 00 47 65 74 4D 65 73 73 61 67 65 41 00 00 00 44 65 73 74 72 6F 79 57 69 6E 64 6F 77 00 00 00 53 65 74 50 69 78 65 6C }
	$a1 = { 00 00 00 00 4B 45 52 4E 45 4C 33 32 2E 64 6C 6C 00 00 55 53 45 52 33 32 2E 64 6C 6C 00 00 47 44 49 33 32 2E 64 6C 6C 00 00 00 00 00 00 00 00 47 65 74 50 72 6F 63 41 64 64 72 65 73 73 00 00 00 47 65 74 4D 6F 64 75 6C 65 48 61 6E 64 6C 65 41 00 00 00 4C 6F 61 64 4C 69 62 72 61 72 79 41 00 00 00 53 6C 65 65 70 00 00 00 47 65 74 56 65 72 73 69 6F 6E 00 00 00 47 65 74 43 6F 6D 6D 61 6E 64 4C 69 6E 65 41 00 00 00 47 65 74 53 74 61 72 74 75 70 49 6E 66 6F 41 00 00 00 47 65 74 41 43 50 00 00 00 43 72 65 61 74 65 54 68 72 65 61 64 00 00 00 44 65 66 57 69 6E 64 6F 77 50 72 6F 63 41 00 00 00 52 65 67 69 73 74 65 72 43 6C 61 73 73 45 78 41 00 00 00 43 72 65 61 74 65 57 69 6E 64 6F 77 45 78 41 00 00 00 47 65 74 53 79 73 74 65 6D 4D 65 74 72 69 63 73 00 00 00 53 68 6F 77 57 69 6E 64 6F 77 00 00 00 47 65 74 44 43 00 00 00 52 65 6C 65 61 73 65 44 43 00 00 00 46 69 6E 64 57 69 6E 64 6F 77 41 00 00 00 47 65 74 4D 65 73 73 61 67 65 41 00 00 00 44 65 73 74 72 6F 79 57 69 6E 64 6F 77 00 00 00 53 65 74 50 69 78 65 6C 00 00 00 00 }
	$a2 = { 00 00 00 00 55 73 65 72 33 32 2E 64 6C 6C 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 47 64 69 33 32 2E 64 6C 6C 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 4B 65 72 6E 65 6C 33 32 2E 64 6C 6C 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 44 65 66 57 69 6E 64 6F 77 50 72 6F 63 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 52 65 67 69 73 74 65 72 43 6C 61 73 73 45 78 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 43 72 65 61 74 65 57 69 6E 64 6F 77 45 78 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 47 65 74 53 79 73 74 65 6D 4D 65 74 72 69 63 73 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 53 68 6F 77 57 69 6E 64 6F 77 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 47 65 74 44 43 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 52 65 6C 65 61 73 65 44 43 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 00 46 69 6E 64 57 69 6E 64 6F 77 41 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 47 65 74 4D 65 73 73 61 67 65 41 00 }

condition:
		$a0 or $a1 or $a2
}

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 3 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the VProtectorvcasm detection rule, including tailored filters and exclusions:

• Scenario: Microsoft Defender Antivirus Real-Time Scanning of VCASM Components

  • Context: The native Microsoft Defender Antivirus engine frequently scans Virtualization Component Assembler (VCASM) binaries in real-time as they are loaded or updated by the hypervisor. This triggers the YARA rule due to the specific signature patterns within the vcasm.dll or related assembly files during routine health checks.
  • Filter/Exclusion: Add a process exclusion for MsMpEng.exe (Microsoft Defender) targeting the file path \Program Files\Microsoft Defender\MpSvc\vcasm*. Alternatively, configure the YARA rule to exclude matches where the parent process is MsMpEng.exe.

• Scenario: Scheduled System Update Deployment via SCCM/Intune

  • Context: During monthly patching cycles, System Center Configuration Manager (SCCM) or Microsoft Intune pushes updates that include virtualization component patches. The deployment agent extracts and installs VCASM modules, causing the YARA rule to fire on the temporary extraction of these files before they are fully integrated into the system registry.
  • Filter/Exclusion: Create a time-based exclusion window (e.g., 02:00 – 06:00 local time) for alerts generated by ccmsetup.exe or intuneagent.exe. Additionally, exclude file paths containing \Windows\CCM\Logs\vcasm* from the detection logic.

• Scenario: VMware vCenter Server Appliance (VCSA) Backup Jobs

  • Context: In environments running VCSA on Windows hosts, scheduled backup jobs initiated by Veeam Backup & Replication or Commvault often access and lock VCASM components to ensure