In the field of information technology, a revolution has been created by the cloud computing which purviews the elements from grid computing, utility computing and autonomic computing to obtain innovative deployment architecture. Cloud computing endeavors smooth access to the cloud data. High performance computing is achieved by storing the data on cloud because the cloud data can be accessed at any time from any place as long as there is network access, this rapid movement towards the cloud has created a major impact on the level of security provided to the cloud storage system data. In this paper a survey on existing approaches to provide security to cloud data is explored and a two-factor data security protection mechanism with factor revocability for cloud storage system has been proposed.