Security is one of the major issues today around the world. Either it is a home user or Corporate User, a small PC or a Server System, nothing is totally secure, lots of issues have been raised regarding security. In this paper, we will be comparing the architectures of the Cloud Providers and how and what Cloud Services they are providing. Here, we will also discuss about the different Security parameters offered by different Cloud Providers and will present the comparative study of security provided at different cloud services viz. Infrastructure as a Service, Platform as a Service and Software as a Service.