Today’s world, technology has become an inevitable part of human life. In fact, during the Covid-19 pandemic, everything from the corporate world to educational institutions has shifted from offline to online. It leads to exponential increase in intrusions and attacks over the internet-based technologies. Distributed denial of service (DDOS) attack is one of the most dangerous attack that could cause devastating effects on the internet. These attacks are becoming more complex and expected to expand in number day after day, rendering detecting and combating these threats challenging. In network security this attack is very dangerous. The main aim of DDOS attack is to collapse the network or server with abnormal traffic to make server unavailable for the legitimate users. In this paper reviews various type of DDOS attacks, Symptoms of DDOS attack, role of botnet on DDOS attack and give some mitigation and prevention technique for DDOS attack.