An abstract from “Security Controls for Computer Systems (U): Report of Defense Science Board Task Force on Computer Security”
With the advent of resource-sharing computer systems that distribute the capabilities and components of the machine configuration among several users or several tasks, a new dimension has been added to the problem of safeguarding computer-resident classified information. The basic problems associated with machine processing of classified information are not new. They have been encountered in the batchprocessing mode of operation and, more recently, in the use of remote job-entry systems; the methods used to safeguard information in these systems have, for the most part, been extensions of the traditional manual means of handling classified documents.
The increasingly widespread use of resource-sharing systems has introduced new complexities to the problem. Moreover, the use of such systems has focused attention on the broader issue of using computers, regardless of the configuration, to store and process classified information.
Resource-sharing systems are those that distribute the resources of a computer system (e.g., memory space, arithmetic units, peripheral equipment, channels) among a number of simultaneous users. The term includes systems commonly called time-sharing, multiprogrammed, remote batch, on-line, multi-access, and, where two or more processors share all of the primary memory, multiprocessing. The principle distinction among the systems is whether a user must be present (at a terminal, for example) to interact with his job (time-sharing, on-line, multi-access), or whether the jobs execute autonomously (multiprogrammed, remote batch). Resource-sharing allows many people to use the same complex of computer equipment concurrently. The users are generally, although not necessarily, geographically separated from the central processing equipment and interact with the machine via remote terminals or consoles. Each user’s program is executed in some order and for some period of time, not necessarily to completion. The central processing equipment devotes its resources to servicing users in turn, resuming with each where it left off in the previous processing cycle. Due to the speeds of modern computers, the individual user is rarely aware that he is receiving only a fraction of the system’s attention or that his job is being fragmented into pieces for processing. Multiprogramming is a technique by which resource-sharing is accomplished. Several jobs are simultaneously resident in the system, each being handled by the various system components so as to maximize efficient utilization of the entire configuration. The operating system1 switches control from one job to another in such a way that advantage is taken of the machine’s most
