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

Hunt Hypothesis

This detection identifies the execution of legacy or potentially obsolete hacking tools, such as the specific eee.exe artifact, which adversaries often leverage to establish a foothold and evade standard signature-based defenses. Proactively hunting for these disclosed artifacts in Azure Sentinel is critical because their known status suggests they may be part of an advanced persistent threat campaign utilizing familiar yet overlooked utilities to maintain stealth within the environment.

YARA Rule

rule sig_238_eee {
	meta:
		description = "Disclosed hacktool set (old stuff) - file eee.exe"
		author = "Florian Roth"
		date = "23.11.14"
		score = 60
		hash = "236916ce2980c359ff1d5001af6dacb99227d9cb"
	strings:
		$s0 = "[email protected]" fullword wide
		$s3 = "C:\\Program Files\\DevStudio\\VB\\VB5.OLB" fullword ascii
		$s4 = "MailTo:[email protected]" fullword wide
		$s5 = "Command1_Click" fullword ascii
		$s7 = "software\\microsoft\\internet explorer\\typedurls" fullword wide
		$s11 = "vb5chs.dll" fullword ascii
		$s12 = "MSVBVM50.DLL" 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 7 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the detection rule “Disclosed hacktool set (old stuff) - file eee.exe”, including suggested filters and exclusions:

• Scenario: Legacy Network Monitoring Agent

  • Context: An enterprise utilizes an older version of a network performance tool (e.g., SolarWinds NPM or PRTG) where the background service executable is named eee.exe (often found in C:\Program Files\LegacyNetMonitor). This process periodically scans ports and generates temporary log files, triggering the “disclosed hacktool” signature due to its network enumeration behavior.
  • Suggested Filter/Exclusion: Create an exclusion based on the full file path hash or directory: Path = C:\Program Files\LegacyNetMonitor\eee.exe AND File Hash = [Insert Specific SHA256]. Alternatively, exclude if the parent process is svchost.exe running under the “LocalSystem” account.

• Scenario: Scheduled Automated Backup Utility

  • Context: A nightly scheduled job (Task Scheduler) runs a custom internal backup script that invokes a legacy utility named eee.exe. This tool is responsible for compressing and archiving old database logs to an on-premises storage server. The rule triggers because the tool performs file I/O operations that mimic data exfiltration or configuration scanning behaviors typical of hacktools.
  • Suggested Filter/Exclusion: Exclude events where the Process Name is eee.exe, the Parent Process is TaskHost.exe (or svchost.exe), and the User Account matches a dedicated service account (e.g., svc-backup-agent). Add a time-based filter to only alert outside of the maintenance window (e.g., 02:00 – 04:00).