Defending DDoS Attacks Using Hidden Markov Models and Cooperative

Abstract. In recent years, distributed denial of service (DDoS) attacks have brought increasing threats to the Internet since attack traffic caused by DDoS attacks can consume lots of bandwidth or computing resources on the Internet and the availability of DDoS attack tools has become more and more easy. However, due to the similarity between DDoS attack traffic and transient bursts of normal traffic, it is very difficult to detect DDoS attacks accurately and quickly. In this paper, a novel DDoS detection approach based on Hidden Markov Models (HMMs) and cooperative reinforcement learning is proposed, where a distributed cooperation detection scheme using source IP address monitoring is employed. To realize earlier detection of DDoS attacks, the detectors are distributed in the mediate network nodes or near the sources of DDoS attacks and HMMs are used to establish a profile for normal traffic based on the frequencies of new IP addresses. A cooperative reinforcement learning algorithm is proposed to compute optimized strategies of information exchange among the distributed multiple detectors so that the detection accuracies can be improved without much load on information communications among the detectors. Simulation results on distributed detection of DDoS attacks generated by TFN2K tools illustrate the effectiveness of the proposed method.