Disclosed hacktool set (old stuff) - file Ie.dll

Hunt Hypothesis

This detection identifies adversaries leveraging legacy Internet Explorer components, specifically the Ie.dll file, to establish persistence or execute malicious tools within the environment. A proactive hunt is essential in Azure Sentinel because outdated IE artifacts often serve as overlooked vectors for attackers to bypass security controls and maintain a low-profile presence on endpoints.

YARA Rule

rule ByPassFireWall_zip_Folder_Ie {
	meta:
		description = "Disclosed hacktool set (old stuff) - file Ie.dll"
		author = "Florian Roth"
		date = "23.11.14"
		score = 60
		hash = "d1b9058f16399e182c9b78314ad18b975d882131"
	strings:
		$s0 = "d:\\documents and settings\\loveengeng\\desktop\\source\\bypass\\lcc\\ie.dll" fullword ascii
		$s1 = "LOADER ERROR" fullword ascii
		$s5 = "The procedure entry point %s could not be located in the dynamic link library %s" fullword ascii
		$s7 = "The ordinal %u could not be located in the dynamic link library %s" fullword ascii
	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 4 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the Disclosed hacktool set (old stuff) - file Ie.dll detection rule, including targeted filters and exclusions:

• Scenario: Legacy Browser Update via Scheduled Task

  • Context: The enterprise utilizes a scheduled task (Microsoft-Windows-IEUpdate) that runs nightly to patch Internet Explorer components. This process often spawns iexplore.exe which loads the legacy Ie.dll in the system directory, triggering the rule due to the “old stuff” signature matching older DLL versions.
  • Filter/Exclusion: Create a whitelist exclusion for the specific file path C:\Windows\System32\Ie.dll when executed by the process usoclient.exe or iexplore.exe. Additionally, exclude events originating from the scheduled task name \Microsoft\Windows\IEUpdate.

• Scenario: Endpoint Protection Scanner Activity

  • Context: During off-hours, the deployed endpoint protection suite (e.g., Microsoft Defender Antivirus or CrowdStrike Falcon) performs a deep scan of browser artifacts. The scanner’s heuristic engine loads Ie.dll to analyze embedded scripts within cached web pages, causing the detection logic to flag it as a potential “hacktool” artifact rather than a standard system file.
  • Filter/Exclusion: Exclude alerts where the parent process is MsMpEng.exe (Defender) or FalconSensor.exe (CrowdStrike). Implement a filter that suppresses the alert if the Ie.dll file hash matches the known good baseline stored in the asset inventory.

• Scenario: Corporate Intranet Portal Rendering

  • Context: Users accessing the internal HR or IT portal via Microsoft Edge (which uses the legacy IE engine for specific ActiveX controls) trigger the loading of Ie.dll. Since many enterprise portals