What role do firewalls and Intrusion Prevention Systems (IPS) play in defending against TCP DDoS?

Firewalls and IPS devices are critical components in a multi-layered defense against TCP DDoS. Firewalls can implement basic rate limiting, block traffic from known malicious IP addresses, or drop packets that don't conform to expected TCP handshake patterns (e.g., ACK packets without a prior SYN). IPS systems offer more advanced protection by: 1) Signature-based detection: Identifying known DDoS attack patterns. 2) Anomaly-based detection: Detecting unusual traffic volumes, packet rates, or source/destination combinations that deviate from normal baselines. 3) Protocol validation: Ensuring TCP packets adhere to protocol standards. 4) Connection tracking: Monitoring the number of concurrent connections and blocking sources that exceed predefined thresholds. They can actively drop malicious packets or throttle suspicious traffic.