Web Shell - file aZRaiLPhp v1.0.php

Hunt Hypothesis

This detection identifies adversaries deploying the specific “aZRaiLPhp v1.0.php” web shell to establish persistent command-and-control access on Azure-hosted web servers. Proactive hunting for this artifact is critical because web shells often serve as a stealthy entry point for lateral movement and data exfiltration that may evade standard signature-based alerts.

YARA Rule

rule webshell_aZRaiLPhp_v1_0 {
	meta:
		description = "Web Shell - file aZRaiLPhp v1.0.php"
		license = "Detection Rule License 1.1 https://github.com/Neo23x0/signature-base/blob/master/LICENSE"
		author = "Florian Roth (Nextron Systems)"
		date = "2014/01/28"
		score = 70
		hash = "26b2d3943395682e36da06ed493a3715"
		id = "393e738a-b4c2-5630-a55f-c3caee4ff75e"
	strings:
		$s5 = "echo \" <font color='#0000FF'>CHMODU \".substr(base_convert(@fileperms($"
		$s7 = "echo \"<a href='./$this_file?op=efp&fname=$path/$file&dismi=$file&yol=$path'><fo"
	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 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the Web Shell - file aZRaiLPhp v1.0.php detection rule, including suggested filters and exclusions:

• Scenario: Automated Deployment via CI/CD Pipeline

  • Context: The DevOps team utilizes GitHub Actions or Jenkins to deploy the aZRaiLPhp utility during nightly build cycles. The pipeline pushes this specific file to the web root (/var/www/html/tools) as part of a standard infrastructure update, triggering the rule immediately upon creation.
  • Filter/Exclusion: Exclude files created by the deployment service account (e.g., svc-deploy-github). Add a filter where Source User equals svc-deploy-github AND File Path contains /tools/aZRaiLPhp v1.0.php.

• Scenario: Scheduled Maintenance Script Execution

  • Context: A scheduled Windows Task Scheduler job (or Linux Cron) runs a diagnostic script every Monday at 2:00 AM that dynamically instantiates or updates the aZRaiLPhp module to check server health. This legitimate administrative task mimics web shell behavior by writing the file during off-hours.
  • Filter/Exclusion: Create an exclusion based on time and process name. Filter out events where Process Name is svchost.exe (Windows) or cron (Linux) AND Event Time falls between 01:30 AM and 04:30 AM on Mondays.

• Scenario: Third-Party Monitoring Agent Installation

  • Context: The enterprise uses Datadog or New Relic agents for application performance monitoring. During an agent upgrade, the monitoring software installs aZRaiLPhp v1.0.php as a custom integration module