Cloud security is the most evolving sub domain of recent research and development in the field of network security. Initially attackers explore the vulnerabilities in cloud system, then it compromise the virtual machines of cloud environment to deploy large scale Distributed Denial of Service(DDoS). DDoS attacks usually include multistep exploitation, low frequency vulnerability scanning and compromising vulnerable virtual machines as zombies, finally attackers deploy DDoS attacks through this zombies. Especially in the Infrastructure as a Service(IaaS) clouds, the detection of zombie attacks are extremely difficult due to the installation of vulnerable applications to their managed virtual machines from cloud user. There are many techniques which are able to manage the zombie attacks efficiently. Here, in this paper we are surveying the techniques which can detect and mitigate the zombie attacks in cloud environment.