Cloud Computing is one of the latest developments in the IT industry, also known as on-demand computing. It provides the full scalability, reliability, high performance and relatively low cost feasible solution as compared to infrastuctures. There are several major cloud computing providrs including Amazon, Google, salesforce, Yahoo, Microsoft and others that are providing cloud computing services. With the increasing popularity of enterprise cloud computing and its public connectivity via the internet, it is the next frontier for viruses, worms, hackers and cyber-terrorist to start probing attacking. Hence though the cloud computing is attracting the enterprises and ornanizations to move there are security risk and challenges for the enterprises and organizations to keep in mind for their virtual infrastructure.