151 TBDT: A New Trust-Based DDoS-Tolerant

DDoS attacks are fatal to the survivability of internet services. Usually DDoS attackers send large number of packets to a victim and congest the victim's bandwidth. As a result, the victim can not supply services to other normal clients until some measures have been taken. Currently popular approaches to DDoS are based on anomaly detection correctly, however it is difficult to differentiate between attacker and normal client absolutely. We motivated this problem and propose a new method defending against DDoS called TBDT. The TBDT assumes that it can identify hospital client, and need not to recognize the attacker. The server will give more trust to hospital client and give less trust to hostile client. Once attacks happened, the server will only supply services to the client whose trust is above the trust threshold. We use simulations to show the effectiveness of TBDT at limiting DDoS floods. The simulation results show that the victim can survive the DDoS attacks.