With the increased availability of the internet and the increased dependency of the people on the internet, cyber-attacks have become more prevalent. DDoS is one such of a cyber-attack. DDoS is a kind of DoS attack which can have many sources and it’s difficult to stop or prevent the attack. In this paper, we are going to present a detailed description about the DoS attack, its types, its effects and its prevention mechanisms.

Keywords : Denial-of-Service, Distributed Denial- of-Service attack.