It is very costly and cumbersome to manage database systems in-house especially for small or medium organizations. Data-as-a-Service (DaaS) hosted in the cloud provides an attractive solution, which is flexible, reliable, easy and economical to operate, for such organizations. However security and privacy issues concerning the storage of the data in the cloud and access via the Internet have been major concerns for many organizations. The data and the human resources are the life blood of any organization. Hence, they should be strongly protected. In this paper, we identify the challenges in securing DaaS model and propose a system called CloudMask that lays the foundation for organizations to enjoy all the benefits of hosting their data in the cloud while at the same time supporting fine-grained and flexible access control for shared data hosted in the cloud.