Cloud encompasses diverse models and technologies. Many of the applications interface with the user via the Web. All the normal security vulnerabilities are just as relevant to applications running on the cloud as they are to applications running on conventional hosting. Another type of security issues related with Physical security where data center to be physically secure against unauthorized access or potential natural disasters.In this paper we discuss about security issues on the cloud especially the DDOS attacks. The distributed environment is prone to more attacks. The DDOS attacks are done by the hacker with help of command prompt or DOS or Linux terminals. The maximum number of attacks in the distributed environment in DDOS attacks.