International Association of Computer Science and Information Technology(IACSIT)
One of the major threats for the Internet's reliability and stability is Distributed Denial-of-Service (DDoS) attack. The attackers are becoming more sophisticated and organized, also several high-profile attacks targeted prominent Websites. These are the prime reasons that gained importance for the study of DDoS attack detection and prevention. It becomes more undetectable if the legitimate HTTP requests are utilized by Application-layer based DDoS attacks to overwhelm the victim resource. Whenever such an attack occurs or mimics the normal flash crowd event of a popular website, then it leads to serious problems.