Cloud computing is the newly emerged technology of distributed computing system. Cloud computing user concentrate on API security and provide services to its consumers in multitenant environment into three layers namely, Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS), with the help of web services. It provides service facilities to its consumers on demand. These service provided can easily invites attacker to attack by SaaS, PaaS and IaaS. Since the resources are gathered at one place in data centers in cloud computing, the DDoS attacks such as HTTP & XML in this environment is dangerous & provides harmful effects and also all consumers will be affected at the same time.