DarkRAT

Hunt Hypothesis

This hypothesis posits that adversaries are deploying the DarkRAT remote access trojan to establish persistence and exfiltrate sensitive data within Azure workloads. Proactive hunting is essential because the current low-severity classification may allow this stealthy malware to evade standard alerting thresholds, necessitating manual correlation of YARA matches with anomalous network egress patterns in Sentinel.

YARA Rule

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

	strings:
		$a = "@1906dark1996coder@"
		$b = "SHEmptyRecycleBinA"
		$c = "mciSendStringA"
		$d = "add_Shutdown"
		$e = "get_SaveMySettingsOnExit"
		$f = "get_SpecialDirectories"
		$g = "Client.My"

	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 5 specific false positive scenarios for the DarkRAT detection rule in an enterprise environment, including suggested filters and exclusions:

• Endpoint Management Agent Updates

  • Scenario: The deployment of a new version or patch by enterprise endpoint management tools (e.g., Microsoft Intune, CrowdStrike Falcon, or Ivanti) often involves the execution of temporary installers that unpack archives and modify registry keys in real-time. These behaviors mimic DarkRAT’s C2 beaconing and file manipulation logic, triggering the YARA signature on the agent’s service process (e.g., CcmExec.exe or FalconSensorService.exe).
  • Suggested Filter: Create an exclusion for processes running under specific trusted user accounts (e.g., NT AUTHORITY\SYSTEM, DOMAIN\Administrator) and restrict the rule to exclude known executable paths within standard management directories, such as C:\Program Files\Microsoft Intune\ or C:\ProgramData\CrowdStrike\.

• Scheduled Software Deployment Jobs

  • Scenario: Automated software distribution tasks scheduled via Task Scheduler (e.g., nightly deployment of Adobe Acrobat updates or Java runtime patches) frequently utilize PowerShell scripts (powershell.exe) to download and extract payloads. If the script invokes a temporary downloader that establishes outbound connections to internal artifact servers, it may match DarkRAT’s network communication patterns and file staging behaviors.
  • Suggested Filter: Exclude events where the parent process is svchost.exe or TaskScheduler and the command line arguments contain specific deployment identifiers (e.g., -DeploymentID, -Source:InternalRepo). Additionally, whitelist outbound traffic to known internal IP ranges used by the Software Distribution Server.

• IT Administration Remote Sessions

  • Scenario: During routine maintenance windows, IT administrators perform remote desktop sessions using