Divya Kuriakose V.Praveena
Network is collection of nodes that interconnect with each other for exchange the Information. This information is required for that node is kept confidentially. Attacker in the network may capture this confidential information and misused. So security is the major issue. There are many security attacks in network. One of the major threats to internet service is DDoS (Distributed denial of services) attack. DDoS attack is a malicious attempt to suspending or interrupting services to target node. Various schemes are developed defence against to this attack. Main idea of this paper is present basis of DDoS attack. Types of DDoS attack, components of DDoS attack, need for Distributed defense system, comparative study of different defense mechanism.