CISSP Security Architecture and Engineering Practice Question
An organization wants to implement a security mechanism that ensures all accesses are mediated and cannot be bypassed, is tamperproof, and is small enough to be verified. This describes which concept?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reference Monitor
The reference monitor is an abstract model that enforces access control with the properties: complete mediation, tamperproof, and verifiable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Trusted Computing Base (TCB)
Why it's wrong here
The Trusted Computing Base (TCB) comprises the entire collection of hardware, firmware, and software components within a computer system whose correct operation is absolutely essential for enforcing the system's security policy. Its integrity is paramount, as any compromise within the TCB could undermine the security of the entire system. While critical for overall system trustworthiness, the TCB is a *set* of components, not a specific, abstract mechanism for mediating access control.
- ✓
Reference Monitor
Why this is correct
The reference monitor is an abstract, conceptual security mechanism that mediates all access attempts by subjects to objects, ensuring strict compliance with the system's defined security policy. For it to be truly effective and secure, it must possess three fundamental properties: it must be tamperproof, always invoked for every access request, and verifiable, allowing its correctness to be mathematically proven. This abstract model serves as the foundational principle for designing secure access control enforcement.
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Trusted Platform Module (TPM)
Why it's wrong here
A Trusted Platform Module (TPM) is a specialized cryptographic hardware chip designed to provide secure storage for cryptographic keys and to perform platform integrity measurements. Its primary functions include secure key generation, storage, and attestation, which verifies the integrity of the system's boot process and software state. While contributing significantly to overall system trust and hardware security, the TPM itself does not directly function as an access control mediation mechanism between subjects and objects.
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Security Kernel
Why it's wrong here
The security kernel represents the concrete, operational implementation of the abstract reference monitor concept within a specific operating system or system architecture. It consists of the hardware, firmware, and software elements directly responsible for enforcing the system's access control policy and isolating security-critical functions. While the security kernel is a vital part of the Trusted Computing Base (TCB) that provides practical security, it is the *realization* of the reference monitor, not the abstract concept itself.
Go deeper
Related to this question
Learn chapter
Security Governance and Principles
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
Key term
Reference monitor
A trusted, always-active component of a computer's operating system that enforces security policies by checking every access request to files, memory, or devices before allowing it.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISSP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISSP exam.