In this Paper we discuss Security issues for Cloud Computing including storage security, data security, and network security and secure virtualization. Cloud computing is an architecture for providing computing service via the internet on demand and pay per use access to a pool of shared resources namely networks, storage, servers, services and applications. This research paper also analyzes the key research and challenges that presents in cloud computing and offers best practices to service providers as well as enterprises hoping to lever age cloud service to improve their bottom line in this severe economic climate.