VProtector11A12vcasm

Hunt Hypothesis

This YARA rule targets the VProtect 11A12vcasm variant, a commercial software protection mechanism often abused by threat actors to obfuscate malicious payloads and evade static analysis. Proactively hunting for this signature in Azure Sentinel helps identify potentially compromised workloads or staged binaries that leverage advanced packers to hide their true intent within the environment.

YARA Rule

rule VProtector11A12vcasm
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 00 00 56 69 72 74 75 61 6C 41 6C 6C 6F 63 00 00 00 00 00 76 63 61 73 6D 5F 70 72 6F 74 65 63 74 5F 32 30 30 35 5F 33 5F 31 38 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 33 F6 E8 10 00 00 00 8B 64 24 08 64 8F 05 00 00 00 00 58 EB 13 C7 83 64 FF 35 00 00 00 00 64 89 25 00 00 00 00 AD CD 20 EB 01 0F 31 F0 EB 0C 33 C8 EB 03 EB 09 0F 59 74 05 75 F8 51 EB F1 B9 04 00 00 00 E8 1F 00 00 00 EB FA E8 16 00 00 00 E9 EB F8 00 00 58 EB 09 0F 25 E8 F2 FF FF FF 0F B9 49 75 F1 EB 05 EB F9 EB F0 D6 E8 07 00 00 00 C7 83 83 C0 13 EB 0B 58 EB 02 CD 20 83 C0 02 EB 01 E9 50 C3 }

condition:
		$a0
}

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: Execution of the vbcasm.exe utility (part of the VBCASM toolset) by a developer or build engineer to compile VBScript source code into a binary .vbs or .exe file for deployment.
  • Filter/Exclusion: Exclude processes where the parent process is cmd.exe, powershell.exe, or msbuild.exe and the file path contains \vbcasm\ or ends with vbcasm.exe.
• Scenario: A scheduled maintenance job or CI/CD pipeline (e.g., Jenkins, Azure DevOps, or GitHub Actions) that invokes a custom build script using vbcasm to package application components.
  • Filter/Exclusion: Exclude events where the process path resides within known CI/CD agent directories (e.g., C:\Jenkins\workspace\, D:\AzureAgent\_work\) or is spawned by java.exe (Jenkins) or node.exe (Azure DevOps).
• Scenario: An IT administrator running a one-off script to convert legacy VBScript automation tools into executable format for distribution to endpoints, often executed from a shared network drive or local admin folder.
  • Filter/Exclusion: Exclude processes where the user account belongs to a specific security group (e.g., IT_Builders, DevOps_Team) and the process path is located in a designated build or admin directory (e.g., C:\AdminTools\, \\fileserver\builds\).
• Scenario: A third-party software installer or updater (e.g., for legacy enterprise apps) that bundles vbcasm to compile on-the-fly scripts during installation or patching.
  • Filter/Exclusion: Exclude processes where the parent process is a known installer executable (e.g., setup.exe, `