1. A system comprising a trusted computing platform and one or more logically protected computing environments, each logically protected computing environment being an operating system compartment associated with at least one service or process supported by said system, the system being arranged to load an operating system into said trusted computing platform and thereafter to load onto said trusted computing platform data defining a predetermined security policy defining security attributes to be applied to one or more of the at least one service or process when said service or process is started.