The use of hardware to provide or enhance security dates from the early days of shared or multi-user computing systems. The Multics system (Multiplexed Information and Computing Service), developed in the 1960s and 1970s, was one of the first to use hardware mechanisms to isolate user processes from each other and from the operating system core and utility functions, and to permit sharing of information according to a well-defined security policy. In 1985 Multics was given a highly coveted B2 "Orange Book" security rating by the National Computer Security Center (NCSC), the first such designation granted by the government to a computer security system. The Multics system was in operation in many organizations and institutions from the mid-1960s until the last Multics installation was decommissioned in 2000.

The history of Multics and subsequent systems has demonstrated that it is difficult to design and implement software...