FortiDDoS is a network behavior anomaly (NBA) prevention system that detects and blocks attacks that intend to disrupt network service by overutilizing server resources. These attacks are commonly referred to as distributed denial of service (DDoS) attacks.

FortiDDoS uses a variety of schemes, including anomaly detection and statistical techniques, to provide nonstop protection, even against attacks that cannot yet be recognized by an attack signature. When FortiDDoS detects an attack, it immediately drops traffic from the offending source, thus protecting the systems it defends from floods.