Cloud computing has a significant role in our daily life. Having many features, it made our life easier. Keeping cloud environment reliable and secure is very essential in order to support large number of users and many smart devices. Now-a-days Cloud computing security is one of the important challenging fields. The biggest security threat for services availability in Cloud Computing is Distributed Denial of Service (DDoS) attack. A major attribute to DDoS attack that hides attacker’s identity is IP address spoofing. With the passing of time DDoS attack becomes powerful, the attack may be minimized if it is detected at first. So we focused on prevention mechanism against the attack for securing the cloud environment.