This document provides an overview of cloud computing from a federal IT security perspective. It discusses the benefits of cloud computing including potential cost savings, increased flexibility and capabilities. It also examines some of the key security challenges for federal agencies in moving to cloud computing environments, such as ensuring proper security controls are in place with cloud vendors and understanding changes to responsibilities. Several federal cloud computing initiatives are also highlighted from agencies such as NASA, VA and DISA. Overall the document presents cloud computing as an evolving model that could modernize federal IT if security risks are adequately addressed.