iKAT toolset file cmd.dll ReactOS file cloaked

Hunt Hypothesis

This detection identifies adversaries utilizing the iKAT toolset to cloak cmd.dll within a ReactOS environment, indicating an attempt to hide command-line execution tools from standard visibility mechanisms. Proactive hunting for this behavior in Azure Sentinel is critical because cloaked system files often serve as stealthy footholds that enable attackers to execute commands and maintain persistence without triggering conventional file integrity alerts.

YARA Rule

rule iKAT_cmd_as_dll {
	meta:
		description = "iKAT toolset file cmd.dll ReactOS file cloaked"
		author = "Florian Roth"
		date = "05.11.14"
		score = 65
		reference = "http://ikat.ha.cked.net/Windows/functions/ikatfiles.html"
		hash = "b5d0ba941efbc3b5c97fe70f70c14b2050b8336a"
	strings:
		$s1 = "cmd.exe" fullword wide
		$s2 = "ReactOS Development Team" fullword wide
		$s3 = "ReactOS Command Processor" fullword wide

		$ext = "extension: .dll" nocase
	condition:
		all of ($s*) and $ext
}

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 4 string patterns in its detection logic.

References

False Positive Guidance

Here are 4 specific false positive scenarios for the iKAT toolset file cmd.dll ReactOS file cloaked rule, including suggested filters and exclusions:

Scenario: Endpoint Detection and Response (EDR) Agent Self-Protection
- Context: Modern EDR solutions like CrowdStrike Falcon, Microsoft Defender for Endpoint, or Carbon Black often inject their own cmd.dll modules into the system namespace to monitor command execution. These agents frequently cloak these files to prevent tampering by malware, mimicking the behavior of a ReactOS-style cloaking mechanism.
- Filter/Exclusion: Create an exclusion for processes originating from trusted EDR service paths (e.g., C:\Program Files\CrowdStrike\ or C:\Windows\System32\Microsoft Defender). Filter alerts where the parent process is the specific EDR service executable (e.g., csagent.exe, MsMpEng.exe) and the file hash matches a known baseline for that agent.
Scenario: Scheduled PowerShell Maintenance Jobs
- Context: Enterprise IT teams often deploy scheduled tasks using Task Scheduler to run maintenance scripts via powershell.exe or cmd.exe. These jobs may utilize custom tooling (like the iKAT suite itself) to perform file integrity checks, temporarily cloaking configuration files or DLLs during execution to ensure atomic updates.
- Filter/Exclusion: Exclude alerts where the parent process is Task Scheduler Service (Schedule.exe) and the command line arguments contain keywords related to maintenance (e.g., -ExecutionPolicy Bypass, specific script names like iKAT_Maintenance.ps1). Additionally, whitelist file paths located in a dedicated administrative tools directory (e.g., C:\Tools\iKAT\).
Scenario: Legacy Application Deployment via SCCM/Intune