The main purpose of the cloud is outsourcing. It is responsible for managing applications and data at runtime. Attackers explore vulnerabilities of cloud system and compromise virtual machine to deploy large scale DDOS. Vulnerability is the weakness which allows attacker to reduce the system access and has capacity to exploit. DDOS is Distributed Denial Of Service that the attackers send a number of requests to the system and compromise the systems called Zombies, they slow down the performance by preventing from getting service.