operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

s architecture a reference monitor concept defines a set of design requirements on a reference validation mechanism, which enforces an access control policy over subjects' (e.g., processes and users) ability to perform operations (e.g., read and write) on objects (e.g., files and sockets) on a system. The properties of a reference monitor are captured by the acronym NEAT, which means: * The reference validation mechanism must be ''Non-bypassable'', so that an attacker cannot bypass the mechanism and violate the security policy. * The reference validation mechanism must be ''Evaluable'', i.e., amenable to analysis and tests, the completeness of which can be assured (verifiable). Without this property, the mechanism might be flawed in such a way that the security policy is not enforced. * The reference validation mechanism must be ''Always invoked''. Without this property, it is possible for the mechanism to not perform when intended, allowing an attacker to violate the security policy. * The reference validation mechanism must be ''

Tamper-proof Tamperproofing, conceptually, is a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system. Since any device or system can be foiled by a person with sufficient knowledge, equipment, and ti ...

''. Without this property, an attacker can undermine the mechanism itself and hence violate the security policy. For example, Windows 3.x and 9x operating systems were not built with a reference monitor, whereas the

Windows NT Windows NT is a proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993. It is a processor-independent, multiprocessing and multi-user operating system. The first version of Win ...

line, which also includes

Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was the direct successor to Windows NT 4.0, and was released to manufacturing on December 15, 1999, and was officiall ...

and

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...

, was designed to contain a reference monitor, although it is not clear that its properties (tamperproof, etc.) have ever been independently verified, or what level of

computer security Computer security, cybersecurity (cyber security), or information technology security (IT security) is the protection of computer systems and networks from attack by malicious actors that may result in unauthorized information disclosure, t ...

it was intended to provide. The claim is that a reference validation mechanism that satisfies the reference monitor concept will correctly enforce a system's access control policy, as it must be invoked to mediate all security-sensitive operations, must not be tampered with, and has undergone complete analysis and testing to verify correctness. The abstract model of a reference monitor has been widely applied to any type of system that needs to enforce access control and is considered to express the necessary and sufficient properties for any system making this security claim. According to Ross Anderson, the reference monitor concept was introduced by James Anderson in an influential 1972 paper. Peter Denning in a 2013 oral history stated that James Anderson credited the concept to a paper he and Scott Graham presented at a 1972 conference.Peter J. Denning
Oral history interview

Charles Babbage Institute The IT History Society (ITHS) is an organization that supports the history and scholarship of information technology by encouraging, fostering, and facilitating archival and historical research. Formerly known as the Charles Babbage Foundation, ...

, University of Minnesota. On pp. 37-38 Denning stated: "James Anderson . . . promoted it in his community, saying that the biggest contribution of that paper was the reference monitor. That became the standard notion in everything he talked about when he was talking about how to make a system more secure." Systems evaluated at B3 and above by the

Trusted Computer System Evaluation Criteria Trusted Computer System Evaluation Criteria (TCSEC) is a United States Government Department of Defense (DoD) standard that sets basic requirements for assessing the effectiveness of computer security controls built into a computer system. The ...

(TCSEC) must enforce the reference monitor concept.

References

See also