System Mechanism for Comparing Security Labels

B.

Because the Reference Monitor is responsible for access control to the objects by the subjects it compares the security labels of a subject and an object.

According to the OIG: The reference monitor is an access control concept referring to an abstract machine that mediates all accesses to objects by subjects based on information in an access control database.

The reference monitor must mediate all access, be protected from modification, be verifiable as correct, and must always be invoked.

The reference monitor, in accordance with the security policy, controls the checks that are made in the access control database.

The following are incorrect: Validation Module.

A Validation Module is typically found in application source code and is used to validate data being inputted.

Clearance Check.

Is a distractor, there is no such thing other than what someone would do when checking if someone is authorized to access a secure facility.

Security Module.

Is typically a general purpose module that prerforms a variety of security related functions.

References: OIG CBK, Security Architecture and Design (page 324) AIO, 4th Edition, Security Architecture and Design, pp 328-328

Wikipedia - http://en.wikipedia.org/wiki/Reference_monitor.

The mechanism that a system uses to compare the security labels of a subject and an object is the Reference Monitor. The Reference Monitor is a security mechanism that controls access to system resources by enforcing access controls and performing security checks. It is a component of the Trusted Computing Base (TCB) that is responsible for enforcing the security policy of the system.

The Reference Monitor is a critical part of the security architecture of a system because it ensures that all access to system resources is authorized and controlled. It checks the security labels of subjects (users, processes, or devices) and objects (files, directories, or devices) to ensure that the access is authorized according to the security policy of the system.

The Reference Monitor acts as an intermediary between the subject and the object and enforces the security policy by controlling access to the object based on the security labels of the subject and the object. It also ensures that the access is logged and audited, so that any unauthorized access attempts can be detected and investigated.

In contrast, the other options listed in the question are not directly related to comparing security labels. The Validation Module typically checks whether a user's credentials are valid before allowing access to a system. The Clearance Check is a process used to determine a user's security clearance level. The Security Module is a generic term that can refer to any component of a security system that provides security services, such as encryption, access control, or authentication.