CISSP Security Architecture and Engineering Practice Question
A government agency requires a security model that prevents users from reading documents at a higher classification level and from writing to documents at a lower classification level. Which model enforces these constraints?
⚠ Common exam trap
CISSP often tests the read/write direction of Bell-LaPadula versus Biba, so the trap is mixing up 'no read up/no write down' (confidentiality) with 'no read down/no write up' (integrity).
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
✓
Bell-LaPadula
Bell-LaPadula is the mandatory access control model focused on confidentiality. Its two core rules are 'no read up' (a subject cannot read data at a higher classification) and 'no write down' (a subject cannot write to a lower classification), which exactly match the government agency's stated constraints. The simple security property and the *-property (star property) enforce these respectively.
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, primarily within military and government hierarchical classification systems. It prevents unauthorized disclosure of information by implementing two core rules: the Simple Security Property (no read up) and the *-Property (no write down). This ensures that subjects can only access information at or below their security clearance level and cannot write information to a lower clearance level, thus maintaining strict confidentiality.
- ✗
Brewer-Nash
Why it's wrong here
The Brewer-Nash model, often referred to as the Chinese Wall model, is specifically designed to prevent conflicts of interest within organizations, particularly in financial or consulting sectors. It dynamically separates users from accessing information that could create a conflict, such as a consultant working for two competing clients. This model focuses on preventing a single individual from accessing information from competing datasets, rather than enforcing hierarchical confidentiality levels.
- ✗
Clark-Wilson
Why it's wrong here
The Clark-Wilson security model is primarily concerned with data integrity, ensuring that data remains accurate and consistent through controlled access and well-formed transactions. It employs concepts like constrained data items (CDIs), transformation procedures (TPs), and integrity verification procedures (IVPs) to maintain data integrity. This model emphasizes separation of duties and auditing to prevent unauthorized modification, making it unsuitable for addressing confidentiality requirements in a hierarchical classification system.
- ✗
Biba
Why it's wrong here
The Biba security model is exclusively focused on ensuring data integrity, aiming to prevent unauthorized modification or corruption of information. It operates with two main rules: the Simple Integrity Axiom (no read down) and the *-Integrity Axiom (no write up), which are the inverse of Bell-LaPadula's rules. This model ensures that subjects cannot write to objects of a higher integrity level or read objects of a lower integrity level, thereby protecting data from contamination by less trusted sources, but it does not address confidentiality.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
Identity and Access Management (IAM)
Key term
Access control
Access control is the security practice of determining who or what is allowed to view, use, or enter a resource, and under what conditions.
Key term
Bell-LaPadula
A formal security model that prevents users from reading information at a higher classification level than their own and from writing information down to a lower classification level.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
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.