LuxNet

Hunt Hypothesis

This hunt hypothesis targets adversary behavior characterized by specific file signatures identified by the LuxNet YARA rule, which may indicate early-stage reconnaissance or benign tool usage within the environment. The SOC team should proactively hunt for these indicators in Azure Sentinel to validate the low-severity alerts against actual threat context and prevent potential false negatives from evolving into significant incidents.

YARA Rule

rule LuxNet : RAT
{
	meta:
		author = " Kevin Breen <kevin@techanarchy.net>"
		date = "2014/04"
		ref = "http://malwareconfig.com/stats/LuxNet"
		maltype = "Remote Access Trojan"
		filetype = "exe"

	strings:
		$a = "GetHashCode"
		$b = "Activator"
		$c = "WebClient"
		$d = "op_Equality"
		$e = "dickcursor.cur" wide
		$f = "{0}|{1}|{2}" 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 4 specific false positive scenarios for the LuxNet detection rule in an enterprise environment, along with suggested filters or exclusions:

• Scenario: Automated Software Deployment via SCCM/Intune

  • Context: During scheduled maintenance windows, System Center Configuration Manager (SCCM) or Microsoft Intune pushes software updates and configuration scripts to endpoints. These deployment agents often spawn temporary processes that mimic the network behavior patterns targeted by the LuxNet YARA rule, particularly when establishing connections to internal distribution points.
  • Filter/Exclusion: Create a whitelist exclusion for process paths containing C:\Windows\CCM\ (SCCM) and C:\Program Files\Microsoft Intune Management Extension\. Additionally, filter out traffic originating from the specific IP ranges of your Software Update Points during defined maintenance hours (e.g., 02:00–04:00 UTC).

• Scenario: Endpoint Detection and Response (EDR) Scanning

  • Context: Real-time scanning engines like CrowdStrike Falcon, SentinelOne, or Microsoft Defender for Endpoint frequently perform deep file system scans. When these agents analyze executable binaries in the C:\Windows\System32 directory, they may trigger the LuxNet signature due to the specific memory footprint and network handshake patterns required to report scan results back to the cloud console.
  • Filter/Exclusion: Exclude known EDR sensor processes from alerting. Specifically, whitelist process names such as csfalcon.exe, S1Agent.exe, and MsMpEng.exe. Ensure the exclusion applies when these processes are accessing files with extensions .exe or .dll within system directories.

• Scenario: Scheduled Backup Operations (Veeam/Commvault)

  • Context: Enterprise backup agents, such as Veeam Agent for Windows or Commvault Simpana, run nightly