An Intrusion Detection System (IDS) is designed to detect and potentially respond to unauthorized access attempts or other security breaches. It monitors network traffic and system activities for malicious activity or policy violations.

Often an IDS is used to notify a human automatically of an issue, while an IPS will even respond to a potential threat automatically without human intervention. Both could be valid answers to this question, but only IDS is a given option. While firewalls and antivirus software play crucial roles in network security, an IDS specializes in detection and is therefore the most appropriate choice for the specified goal.