Abstract: “One of the greatest threats that network security faces nowadays is Distributed Denial of Service attacks. A newer version of the Denial of Service attack, also called Distributed Denial of Service attack or DDoS. In a distributed denialof- service (DDoS) attack, an attacker may use your computer to attack another computer. An attacker may attempt to: “flood” a network and thus reduce a legitimate user‟s bandwidth, prevent access to a service, or disrupt service to a specific system or a user. I”

Keywords: Distributed Denial of Service, Host -based Intrusion Detection , Flood attack, Simulation