Security Policy Definition and Enforcement in Distributed Systems

Security in computer systems is concerned with protecting resources from unauthorized access while ensuring legitimate requests can be satisfied all the time. The recent growth of computer systems both in scale and complexity poses tremendous management challenges. Policy-based systems management is a very promising solution in this scenario. It allows the separation of the rules that govern the behavior choices of a system from the provided functionality, and can be adapted to handle a large number of system elements. In the past two decades there have been many advances in the field of policy research. Although existing solutions in centralized systems are well-established, they do not work nearly as well in distributed environments because of scalability, network partitions, and the heterogeneity of the endpoints. This dissertation contributes to this endeavor by proposing three novel techniques to address the problem of security policy definition and enforcement in large-scale distributed systems. To correctly enforce service and security requirements from users who have no intimate knowledge of the underlying systems, we introduce the first distributed policy refinement soluti