CISSP Security Architecture and Engineering Practice Question
A government agency requires a security model that prevents users from reading documents classified above their clearance level and from writing classified information to lower-level systems. Which model enforces these constraints?
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
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Bell-LaPadula
The Bell-LaPadula model is a state machine model that enforces confidentiality via the *no read up* (simple security property) and *no write down* (*-property) rules.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Bell-LaPadula
Why this is correct
The Bell-LaPadula security model is specifically designed to enforce confidentiality in multi-level security systems, making it ideal for government agencies dealing with classified information. It operates on two core rules: the Simple Security Property (no read up) and the *-Property (no write down). These rules prevent subjects from accessing information at a higher security level than their own and from writing information to a lower security level, thereby ensuring that classified data remains protected from unauthorized disclosure.
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Biba
Why it's wrong here
The Biba integrity model is fundamentally concerned with preventing unauthorized modification of information, prioritizing data integrity over confidentiality. Its two primary rules are the Simple Integrity Property (no read down) and the *-Integrity Property (no write up). These rules ensure that subjects cannot read data of a lower integrity level or write to a higher integrity level, preventing the corruption of high-integrity information by less trusted sources.
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Brewer-Nash
Why it's wrong here
The Brewer-Nash model, often called the Chinese Wall model, is designed to prevent conflicts of interest within organizations, particularly in financial services. It achieves this by creating dynamic separation, ensuring that a subject who has accessed information about one company in a conflict-of-interest class cannot then access information about a competing company within the same class. This model focuses on access control based on prior access history rather than hierarchical security levels for confidentiality.
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Clark-Wilson
Why it's wrong here
The Clark-Wilson integrity model focuses on maintaining data integrity through well-formed transactions and separation of duties. It employs constrained data items (CDIs) and transformation procedures (TPs) to ensure that only authorized operations can modify data, moving it from one valid state to another. Certification rules and enforcement rules govern these processes, ensuring that data remains consistent and accurate, which is distinct from protecting against unauthorized information disclosure.
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Related to this question
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Security Governance and Principles
Key term
Security model
A security model is a formal framework that defines how subjects (users, processes) can access objects (files, resources) based on rules, ensuring confidentiality, integrity, and availability.
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
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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.