Final answer:
An Intrusion Prevention System (IPS) detects unauthorized intruders and takes action to stop them, distinguishing it from an IDS, which only detects and alerts but doesn't take preventative actions.
Step-by-step explanation:
The type of system that detects unauthorized intruders and then takes action to stop them from proceeding is an Intrusion Prevention System (IPS). An IPS continuously monitors network traffic and has the capability to automatically block potential threats. Unlike an Intrusion Detection System (IDS), which only detects and alerts on potential security breaches, an IPS actively takes steps to prevent the attack. An IDS works by monitoring network traffic and looking for suspicious activities or patterns that indicate a potential intrusion.
Once an intruder or unauthorized activity is detected, the IDS can take various actions to stop the intrusion, such as blocking the suspicious IP address, sending an alert to the network administrator, or even automatically initiating countermeasures.