VxCaz1204

Hunt Hypothesis

This rule detects the presence of the VxCaz1204 YARA signature, which identifies specific malicious code patterns or known variants of a low-severity threat within the environment. Proactively hunting for this indicator allows the SOC team to identify dormant or early-stage compromises in Azure Sentinel before they escalate into more impactful incidents or lateral movement.

YARA Rule

rule VxCaz1204
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 [2] 5E 83 EE 03 1E 06 B8 FF FF CD 2F 3C 10 }

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

• Antivirus/EDR Signature Updates: The rule likely matches binary patterns or strings associated with specific malware families (e.g., Cobalt Strike, Mimikatz, or common RATs). Legitimate security agents like CrowdStrike Falcon, Carbon Black, or Microsoft Defender for Endpoint frequently load updated signature databases or helper executables that may contain overlapping byte sequences or string artifacts.

  • Filter: Exclude processes where the parent is the security agent service (e.g., FalconSensor.exe, CbService.exe, MsMpEng.exe) or where the image path resides in the vendor’s installation directory (e.g., C:\Program Files\CrowdStrike\, C:\Program Files\WDS\).

• Third-Party Remote Access Tools: Enterprise IT teams often deploy legitimate remote management tools such as TeamViewer, AnyDesk, BeyondTrust Connect:Enterprise, or ScreenConnect. These tools may use similar cryptographic libraries, string constants, or memory structures that trigger generic YARA rules designed to catch backdoors or RATs.

  • Filter: Exclude known trusted remote access executables (e.g., TeamViewer.exe, AnyDesk.exe, Connect.exe) and their associated service processes, or whitelist the specific vendor’s installation directory.

• Development and Testing Environments: Developers and QA engineers running local instances of Visual Studio Code, JetBrains IntelliJ, or Docker Desktop may load debuggers, test harnesses, or containerized microservices that mimic malicious behavior patterns (e.g., loading dynamic libraries, creating named pipes, or using specific API calls).

  • Filter: Exclude processes running from development tool directories (e.g., C:\Program Files\Microsoft Visual Studio\, C:\Users\<user>\AppData\Local\Programs\) or exclude hosts tagged as dev, `