The Research On Active Distributed Defense System Against DDoS Attacks

With the development and popularity of information technology, network security has become a hot issue in the Internet. Currently, the impact of DDoS has turned into a serious problem to influence functions of the Internet. The characteristic is an explicit attempt by an attacker to prevent legitimate users of certain service from accessing to the particular resources.The paper firstly introduces the theory of DDoS, and analyses both active and passive defense mechanism. Particularly the strategy and methods of active defense mechanism are discussed. Then one method based on statistics to detect the abnormity of network is thoroughly introduced. Relying on SSFNet simulation software, the paper sets up corresponding network environment, and simulates a sort of DDoS attack-TCP SYN FLOOD attack. Through the collection and management of data in the simulation experiment, the analysis of network traffic when the attack occurs, and as well as adjustment of the scheme are given. Then the paper makes a comparison of the network traffic based on different capacity of the server and different degree of the attack. Finally the attack characteristics of TCP SYN FLOOD attack are summarized at the end of the paper.