DDoS (distributed denial of service) attacks aim to make online services unavailable by flooding them with malicious traffic from many compromised systems, but detection and prevention tools like firewalls, ACLs, and traffic scrubbing centers can help mitigate attacks by filtering unauthorized traffic and inspecting packets for signs of anomalies. Network administrators must carefully monitor traffic patterns, update access control lists, and work with internet service providers who can implement traffic redirection during attacks to successfully defend against DDoS threats.