Which tool can assist in monitoring for unauthorized access attempts on a Web server?

An Intrusion Detection System (IDS) is specifically designed to monitor network traffic and user activity for signs of unauthorized access attempts or other suspicious behavior. It analyzes incoming and outgoing traffic against a set of predefined rules or patterns, looking for anomalies that might indicate intrusions or security breaches. This capability is essential for identifying attempts to compromise a Web server and allows administrators to respond to potential threats proactively.

The other options serve different purposes. Antivirus software focuses on detecting and removing malware from an individual system, rather than monitoring network security events. A firewall provides a barrier between trusted internal networks and untrusted external networks, controlling incoming and outgoing traffic based on security rules but does not actively monitor for suspicious activity. A Content Management System (CMS) is used to create and manage digital content but does not provide security monitoring capabilities related to unauthorized access attempts.

Therefore, the Intrusion Detection System is the most suitable choice for monitoring unauthorized access attempts on a Web server.