International Journal of Web Applications Akash Sharma, Deepanshu Batra, Rajat Pandey, Priti Narwal, Vinay Kumar 10 3 2018 https://doi.org/10.6025/ijwa/2018/10/3/91-99 http://www.dline.info/ijwa/fulltext/v10n3/ijwav10n3_2.pdf Since past few years, there has been a rapid increase in use of attacks or cyber crime over the cyber space and one of the most common attacks used is the distributed denial of service attack. These attacks leads for use in the variety of both the attacks and the defence approaches. In this paper, classification of the available mechanisms which are proposed in the literature on how to keep the cyber space away from the possible DDoS attacks and discuss the strong and weak points of each mechanism. This provides the better understanding of the problem and enables a security administrator to effectively equip his storages with proper prevention mechanisms for fighting against DDoS attacks. The paper investigated multiple nature of the problem and look for its causes, further presenting brief insights and suggested approaches for defending against DDoS attack.