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?
⚠ Common exam trap
CISSP often tests the confusion between Bell-LaPadula (confidentiality: no read up, no write down) and Biba (integrity: no read down, no write up) — candidates who memorize only one direction pick the wrong model.
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, enforcing 'no read up' (simple security property) and 'no write down' (star property). These two rules exactly match the requirement: users cannot read above their clearance and cannot write classified data to lower levels. Biba, Brewer-Nash, and Clark-Wilson address integrity or conflict-of-interest, not confidentiality.
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.
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
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
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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.