Since the phenomenon of cloud computing was proposed, there is a continuous interest for research across the globe. Cloud computing has been seen as entire of the technology that poses the next-generation computing revolution and rapidly becomes the hottest topic in the field of IT. This fast move towards Cloud computing has sustained concerns on a fundamental point for the success of information systems, communication, virtualization, data availability and integrity, public auditing, scientific application and information security. Therefore, cloud computing research has attracted tremendous interest in recent years. In this paper, we aim to precise the current issues of Cloud computing. We have discussed the paper in two-fold: first we discuss the cloud computing architecture and the numerous services it offered. Secondly we highlight several security issues in cloud Computing based on its service layer.