Vertex

Hunt Hypothesis

This detection targets adversary behavior involving specific file artifacts identified by the Vertex YARA signature, which may indicate early-stage reconnaissance or persistence mechanisms within the environment. Proactively hunting for these indicators in Azure Sentinel is essential to validate the rule’s efficacy and uncover potential low-severity threats that automated alerts might overlook before they escalate into significant incidents.

YARA Rule

rule Vertex : RAT
{

	meta:
		author = " Kevin Breen <[email protected]>"
		date = "2014/04"
		ref = "http://malwareconfig.com/stats/Vertex"
		maltype = "Remote Access Trojan"
		filetype = "exe"

	strings:
		$string1 = "DEFPATH"
		$string2 = "HKNAME"
		$string3 = "HPORT"
		$string4 = "INSTALL"
		$string5 = "IPATH"
		$string6 = "MUTEX"
		$res1 = "PANELPATH"
		$res2 = "ROOTURL"

	condition:
		all of them
}

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 8 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the Vertex detection rule in an enterprise environment, including suggested filters and exclusions:

• Automated Software Deployment via SCCM/Intune

  • Scenario: The Vertex YARA rule triggers on legitimate installer processes (e.g., msiexec.exe or setup.exe) launched by Microsoft Endpoint Configuration Manager (SCCM) or Intune during scheduled patching windows. These installers often unpack temporary files containing the specific code patterns identified by the “Vertex” signature, mimicking suspicious activity.
  • Filter/Exclusion: Add an exclusion for processes where the parent process is ccmexec.exe (SCCM) or IntuneManagementExtension.exe, specifically targeting file paths within %ProgramFiles%\Microsoft Intune\Agent or %ProgramData%\Microsoft\SMS Client.

• Scheduled Antivirus Definition Updates

  • Scenario: The rule fires when the enterprise endpoint protection suite (e.g., CrowdStrike Falcon, SentinelOne, or McAfee) performs its daily definition update. The update mechanism extracts compressed archives containing new detection signatures that match the “Vertex” YARA pattern before they are fully integrated into the security engine.
  • Filter/Exclusion: Exclude alerts where the process name matches known AV service executables (e.g., cs.exe, s1service.exe, McShield.exe) and the file hash corresponds to a verified vendor signature database update, rather than an unknown binary.

• CI/CD Pipeline Artifact Extraction

  • Scenario: In development environments, build agents (such as Jenkins, GitLab Runner, or Azure DevOps Agents) extract Docker images or application artifacts during continuous integration builds. The “Vertex” rule detects the unpacking of these artifacts (often containing compiled binaries with similar structural signatures) on the build server’s temporary directories (/tmp,