ExeGuarderv18Exeiconcom

Hunt Hypothesis

This detection identifies potential malicious executable activity by analyzing icon composition anomalies that may indicate file masquerading or obfuscation techniques used by adversaries to evade standard signature-based defenses. Proactive hunting for this behavior in Azure Sentinel is essential to uncover low-severity threats that often bypass initial alerts, allowing the SOC team to investigate subtle indicators of compromise before they escalate into significant incidents.

YARA Rule

rule ExeGuarderv18Exeiconcom
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 83 C4 D0 53 56 57 8D 75 FC 8B 44 24 30 25 00 00 FF FF 81 38 4D 5A 90 00 74 07 2D 00 10 00 00 EB F1 89 45 FC E8 C8 FF FF FF 2D B2 04 00 00 89 45 F4 8B 06 8B 40 3C 03 06 8B 40 78 03 06 8B C8 8B 51 20 03 16 8B 59 24 03 1E 89 5D F0 8B 59 1C 03 1E 89 }

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 4 specific false positive scenarios for the ExeGuarderv18Exeiconcom detection rule, including suggested filters and exclusions:

• Scenario: Automated Deployment via Microsoft Endpoint Configuration Manager (SCCM)

  • Context: During scheduled maintenance windows, SCCM deploys applications to thousands of endpoints. The deployment engine often extracts executables with embedded icons from a compressed package before launching them, which can trigger the YARA rule if the icon structure matches known patterns in the rule’s signature.
  • Filter/Exclusion: Add an exclusion for processes spawned by ccmsetup.exe or wuaengine.exe. In your SIEM logic, filter out alerts where the parent process name contains “Microsoft Endpoint Configuration Manager” and the user context is a local system account (e.g., NT AUTHORITY\SYSTEM).

• Scenario: Antivirus Real-Time Protection Scanning by CrowdStrike Falcon

  • Context: The CrowdStrike Falcon sensor performs real-time scanning of executable files in the %TEMP% directory. When a user downloads and launches an installer, the sensor creates a temporary copy with specific icon metadata that mimics the signature detected by ExeGuarderv18Exeiconcom.
  • Filter/Exclusion: Exclude alerts where the file path resides within the CrowdStrike installation directory (e.g., C:\Program Files\CrowdStrike\) or where the process name is csfalcon.exe and csagent.exe. Additionally, filter for events occurring during the specific “Real-Time Scan” phase of the agent’s activity log.

• Scenario: Scheduled Group Policy Application Updates

  • Context: A nightly scheduled task runs to update application icons or refresh user profiles via a custom PowerShell script (UpdateIcons.ps1). This script iterates through .exe files in the `C:\ProgramData