Exam CISSP topic 1 question 294 discussion

D. Reference monitor The reference monitor is a fundamental security component responsible for enforcing access controls and ensuring that security policies are followed. It acts as a trusted entity that mediates all accesses to objects (such as files or resources) and checks whether a requesting entity (user or process) has the necessary permissions to perform the requested action on the object. The reference monitor enforces security policies and access controls based on predefined rules and security mechanisms. It is a critical part of access control systems in computer security.

Reference monitors A secure system requires some component that mediates and enforces access controls. The actual hardware or software implementations vary, but they're all implementations of an abstract computing concept called a reference monitor. Whenever a subject tries to act upon an object, the reference monitor validates the subject's authorization against the specific action. It also must protect objects from any kind of unauthorized modification. A secure reference monitor must have four properties, often collectively referred to as NEAT. Non-bypassable An attacker cannot simply go around it to violate security. Evaluable Testable enough that you can verify (assure) its trustworthiness. Typically, small, well-defined components are more evaluable than large, loosely defined ones. Always Invoked No sensitive operations occur without the reference monitor's involvement. Tamper-proof An attacker cannot compromise its internal functions.

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.

Answer D "A set of design requirements on a reference validation mechanism that, as a key component of an operating system, enforces an access control policy over all subjects and objects. A reference validation mechanism is always invoked (i.e., complete mediation), tamperproof, and small enough to be subject to analysis and tests, the completeness of which can be assured (i.e., verifiable)." https://csrc.nist.gov/glossary/term/reference_monitor