The innovation of Internet has enhanced the use of computers and mobile devices. As a result a large amount of data is being generated on daily basis. Information Technology infrastructure continues to grow with evolving technology and as a result a new business model has emerged known as "Cloud Computing". It is set of resources and services which are obtainable through the Internet. Cloud services are provided from data centers which are located all over the world. It is one of the most electrifying technologies because it has reduced cost related to the computing whereas increased flexibility, scalability, mobility and enhanced storage. The rapid growth in the field of "Cloud Computing" similarly upsurges severe security concerns. Security is actually one of the widely discussed issues in cloud computing, other issues being Availability, Integrity etc. Many research papers have proposed solutions to these problems.

This paper provides a critical review of the recent work done in the area of security by doing a thorough review of recent work in this area. Finally, we propose a model to improve security in cloud architecture.