Sub7Nation

Hunt Hypothesis

This detection targets adversaries utilizing the Sub7Nation malware family to establish persistent command and control channels within networked endpoints. Proactive hunting in Azure Sentinel is essential to identify early-stage infections that may evade standard signature-based defenses, allowing analysts to map lateral movement before data exfiltration occurs.

YARA Rule

rule Sub7Nation : RAT
{
	meta:
		author = " Kevin Breen <[email protected]>"
		date = "2014/04"
		ref = "http://malwareconfig.com/stats/Sub7Nation"
		maltype = "Remote Access Trojan"
		filetype = "exe"

	strings:
		$a = "EnableLUA /t REG_DWORD /d 0 /f"
		$b = "*A01*"
		$c = "*A02*"
		$d = "*A03*"
		$e = "*A04*"	
		$f = "*A05*"
		$g = "*A06*"
		$h = "#@#@#"
		$i = "HostSettings"
		$verSpecific1 = "sevane.tmp"
		$verSpecific2 = "cmd_.bat"
		$verSpecific3 = "a2b7c3d7e4"
		$verSpecific4 = "cmd.dll"

		
	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 13 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the Sub7Nation detection rule in an enterprise environment, along with suggested filters and exclusions:

• Endpoint Protection Policy Updates via CrowdStrike Falcon

  • Scenario: The CrowdStrike Falcon Sensor performs a scheduled daily policy refresh, which involves downloading and executing configuration scripts that mimic Sub7Nation’s command-line argument structure (specifically the use of powershell.exe -EncodedCommand with base64 payloads). This often triggers during off-hours maintenance windows.
  • Filter/Exclusion: Create an exclusion based on the parent process name (C:\Program Files\CrowdStrike\csfalcon.exe) and restrict the alert to only trigger if the command line contains specific keywords not associated with standard policy updates (e.g., exclude commands containing UpdatePolicy or SyncConfig).

• Microsoft Endpoint Configuration Manager (SCCM) Software Deployment

  • Scenario: During a major software rollout, SCCM executes application installation packages using msiexec.exe wrapped in PowerShell scripts. These scripts frequently invoke remote management tasks that generate network connections and file modifications indistinguishable from Sub7Nation’s initial beaconing behavior, particularly when deploying the “Sub7” monitoring agent itself to new workstations.
  • Filter/Exclusion: Exclude events where the process path starts with C:\Windows\CCM\ or C:\Program Files\Microsoft Configuration Manager\. Additionally, filter by user context to exclude actions running under the SYSTEM account during known deployment maintenance windows (e.g., 02:00–04:00 UTC).

• Automated Compliance Scanning with Qualys Cloud Agent

  • Scenario: The Qualys Cloud Agent runs a scheduled vulnerability assessment that scans registry keys and file integrity. This process spawns temporary PowerShell instances to generate detailed compliance reports, which often utilize