Disclosed hacktool set (old stuff) - file Install.exe

Hunt Hypothesis

This detection identifies adversaries leveraging legacy or repurposed hacking tools disguised as standard installation executables to establish a foothold within the environment. Proactively hunting for this behavior in Azure Sentinel is critical to uncover stealthy initial access attempts that may evade signature-based defenses by mimicking benign software deployment patterns.

YARA Rule

rule Jc_ALL_WinEggDropShell_rar_Folder_Install_2 {
	meta:
		description = "Disclosed hacktool set (old stuff) - file Install.exe"
		author = "Florian Roth"
		date = "23.11.14"
		score = 60
		hash = "95866e917f699ee74d4735300568640ea1a05afd"
	strings:
		$s1 = "http://go.163.com/sdemo" fullword wide
		$s2 = "Player.tmp" fullword ascii
		$s3 = "Player.EXE" fullword wide
		$s4 = "mailto:[email protected]" fullword ascii
		$s5 = "S-Player.exe" fullword ascii
		$s9 = "http://www.BaiXue.net (" fullword wide
	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 6 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the “Disclosed hacktool set (old stuff) - file Install.exe” rule, including suggested filters and exclusions:

• Scenario: Legacy Software Deployment via SCCM

  • Context: The enterprise uses Microsoft Endpoint Configuration Manager (SCCM) to push legacy applications. During a maintenance window, the deployment agent executes Install.exe from a network share (\\fileserver\apps\legacy_tool) to install an older version of a patch management utility that predates modern signing standards.
  • Suggested Filter: Exclude processes where the parent process is ccmsetup.exe (SCCM) and the file path contains \apps\legacy_tool. Additionally, filter based on the specific SHA256 hash of the known good Install.exe.

• Scenario: Scheduled Maintenance for Antivirus Definitions

  • Context: A scheduled task runs nightly at 02:00 AM to update an older third-party endpoint protection suite. The updater service launches a local utility named Install.exe located in C:\Program Files\LegacyAV\Updater\ to refresh definition databases, which the rule flags as a “hacktool” due to its generic naming convention.
  • Suggested Filter: Create an exclusion for files residing in C:\Program Files\LegacyAV\* where the process name is Install.exe. Ensure the filter applies only when the parent process is svchost.exe or a specific service executable (e.g., avservice.exe).

• Scenario: IT Admin Manual Installation via Remote Desktop

  • Context: An IT administrator logs in via RDP to a jump host and manually runs a silent installation script for a new internal reporting tool. The script invokes a generic installer named Install.exe stored on the local desktop or a temporary folder (`C:\Temp\