PythoRAT

Hunt Hypothesis

This hunt targets adversaries leveraging Python-based remote access tools to establish persistent command-and-control channels within the environment. Proactively searching for these specific YARA signatures in Azure Sentinel is essential to identify early-stage lateral movement and data exfiltration activities that may evade standard signature-based detections due to their low severity classification.

YARA Rule

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

	strings:
		$a = "TKeylogger"
		$b = "uFileTransfer"
		$c = "TTDownload"
		$d = "SETTINGS"
		$e = "Unknown" wide
		$f = "#@#@#"
		$g = "PluginData"
		$i = "OnPluginMessage"

	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 8 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the PythoRAT detection rule in an enterprise environment, along with suggested filters or exclusions:

• Automated Python Script Execution by IT Operations Teams

  • Scenario: Enterprise administrators frequently deploy custom Python automation scripts (e.g., using ansible, fabric, or internal tooling) to perform routine maintenance like log rotation, user provisioning, or database backups. These scripts often invoke the standard python.exe binary with arguments that match the PythoRAT YARA signatures for script loading and network initialization.
  • Filter/Exclusion: Exclude processes where the parent process is a known automation controller (e.g., AnsibleController.exe, ServiceHost.exe running under the “Network Service” account) or where the file path matches the organization’s standard deployment directory (e.g., C:\Program Files\InternalTools\Scripts\*).

• CI/CD Pipeline Build Agents Running Python Tasks

  • Scenario: In DevOps environments, build agents (such as Jenkins, GitLab Runners, or Azure DevOps) execute Python-based unit tests, code quality scans (using tools like SonarQube or Pylint), and container image builds. These activities involve spawning multiple python.exe instances that download dependencies from internal artifact repositories, triggering the RAT’s “network communication” and “script execution” logic.
  • Filter/Exclusion: Create a whitelist for process paths located within specific CI/CD agent directories (e.g., C:\Program Files\Jenkins\workspace\* or /var/lib/gitlab-runner/caches/*) and exclude events where the user context is a dedicated service account like jenkins-agent or gitlab-runner.

• Scheduled Data Analytics and Reporting Jobs

  • Scenario: Business Intelligence