Cloud computing is rising as a promising business concept and has undergone tremendous growth since the last few years in the IT segment of industries. With the increasing number of companies resorting to employ resources in the cloud, the protection of the users’ data is a significant and prime issue of concern. Since a long time, Distributed Denial of Service (DDoS) attacks have been considered as one of the most hazardous attack on Cloud Networks and its security. Companies that are highly dependent on the internet for their business and transactions can face severe problems during the DDoS attacks. This is a critical matter which calls for an effectual method or system that can promisingly reduce the impact of the DDoS attacks. This paper focuses on the DDoS attacks on Cloud and studies the contemporary Intrusion Detection Systems existing to tackle them.