VcasmProtector1112vcasm

Hunt Hypothesis

This detection identifies the presence of the Vcasm Protector 1112 protection mechanism, which is frequently employed by malware to obfuscate executable code and evade static analysis. Proactively hunting for this signature in Azure Sentinel allows the SOC team to uncover potentially protected malicious binaries that may bypass standard heuristic scans, ensuring early visibility into sophisticated evasion tactics.

YARA Rule

rule VcasmProtector1112vcasm
{
      meta:
		author="malware-lu"
strings:
		$a0 = { EB 0B 5B 56 50 72 6F 74 65 63 74 5D }

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 5 specific false positive scenarios for the VcasmProtector1112vcasm detection rule, including targeted filters and exclusions:

• Scenario: The Microsoft System Center Configuration Manager (SCCM) client service (ccmexec.exe) performs a scheduled software update or application deployment task. During this process, it unpacks protected payloads that match the Vcasm protector signature within the temporary cache directory.

  • Filter/Exclusion: Exclude processes running under C:\Windows\CCM\ where the parent process is ccmexec.exe and the file path contains \AppData\Local\Temp\.

• Scenario: The Kaspersky Endpoint Security or Symantec Endpoint Protection antivirus engine scans a large archive (e.g., .7z or .zip) containing a legacy application installer. The YARA rule triggers on the embedded Vcasm-protected executable inside the archive during the extraction phase by the AV service (kav.exe or rtvscan64).

  • Filter/Exclusion: Create an exclusion for file paths ending in .7z, .zip, or .cab when scanned by known AV services, specifically excluding the rule if the parent process is a recognized security vendor executable.

• Scenario: An automated PowerShell script executed via Windows Task Scheduler runs nightly to distribute internal line-of-business (LOB) applications. The script uses Invoke-WebRequest to download and extract a protected installer (setup.exe) which contains the Vcasm signature, triggering the rule during the extraction phase by PowerShell (powershell.exe).

  • Filter/Exclusion: Exclude alerts where the parent process is powershell.exe (with command line arguments containing -ExecutionPolicy Bypass) and the file extension is .exe, provided the script name matches known internal deployment scripts.