iLUCRYPTv4018exe

Hunt Hypothesis

This hypothesis targets the execution of the iLUCRYPT ransomware variant, specifically version 4018, which is known for encrypting files and dropping a unique executable payload. Proactively hunting for this specific binary in Azure Sentinel allows the SOC to identify early-stage ransomware deployment or lateral movement attempts before widespread encryption occurs, particularly in environments where endpoint detection may miss low-severity or obfuscated executions.

YARA Rule

rule iLUCRYPTv4018exe
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 8B EC FA C7 [4] 4C 4C C3 FB BF [2] B8 [2] 2E [2] D1 C8 4F 81 }

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

• Scenario: An application deployment or patching tool (e.g., SCCM, Intune, or Ansible) copies the iLUCRYPTv4018.exe binary to a user’s %TEMP% or %APPDATA% directory to execute a specific cryptographic utility or license validation step.
  • Filter/Exclusion: Exclude executions where the parent process is a known deployment agent (e.g., CcmExec.exe, IntuneEnrollmentUtil.exe, ansible-playbook.exe) AND the file path contains \Temp\ or \AppData\Local\Temp\.
• Scenario: A developer or IT admin runs the iLUCRYPTv4018.exe tool manually from a USB drive or network share to encrypt/decrypt a large data file for backup or transfer, often from a non-standard directory like D:\Tools\ or \\fileserver\tools\.
  • Filter/Exclusion: Exclude if the image path starts with a known administrative tool directory (e.g., D:\Tools\, C:\Program Files (x86)\ILU\) OR if the parent process is cmd.exe/powershell.exe initiated by a user in the “IT Admins” or “Developers” security group.
• Scenario: A scheduled task or service (e.g., a custom backup script or data retention job) invokes iLUCRYPTv4018.exe to encrypt logs or archives before moving them to cold storage. The executable resides in a service-specific directory like C:\Program Files\BackupService\bin\.
  • Filter/Exclusion: Exclude if the image path is under C:\Program Files\ or C:\Program Files (x86)\ AND the parent process is svchost.exe (for