An intrusion prevention system (IPS) not only detects malicious activities but actively blocks them from causing harm to the network. While an intrusion detection system (IDS) also monitors for potentially malicious activity, it differs from an IPS because it does not block the activity but rather alerts the administrator. A firewall is designed to block unauthorized access based on predetermined security rules, not specifically to handle post-detection activities like an IPS. A proxy server, conversely, facilitates requests between the client and the server primarily for anonymity and can perform content filtering but does not directly act on intrusion attempts like an IPS.