The 'Unusual Web Server Command Execution' rule is designed to detect atypical command executions that originate from web server processes on Linux systems. By utilizing the 'new_terms' rule type, it identifies deviations from normal command execution behavior that could indicate malicious activity. Web servers such as Apache, Nginx, and others are frequently exploited by attackers to maintain persistence within compromised systems. This rule analyzes process events, focusing particularly on those spawned from specific parent processes related to web servers or executed by specific users associated with these services. The query targets unusual command-line arguments, especially those invoking common shell interpreters, while excluding known valid execution patterns. This enables the identification of potential threats like web shells or other forms of unauthorized command execution that are indicative of persistence tactics employed by attackers.