This CISSP practice question tests your understanding of security architecture and engineering. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which security model focuses on preventing unauthorized access by enforcing a 'no read up, no write down' rule?
Clark-Wilson
Why wrong: Clark-Wilson is an integrity model based on transformation procedures and constrained data items.
Bell-LaPadula
Correct. Bell-LaPadula is the confidentiality model with no read up and no write down.
Biba
Why wrong: Biba is an integrity model that enforces 'no read down' and 'no write up'.
Brewer-Nash
Why wrong: Brewer-Nash (Chinese Wall) is a confidentiality model that prevents conflict of interest.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Bell-LaPadula
The Bell-LaPadula model is a formal state machine model for enforcing access control in government and military systems. Its core rule, 'no read up' (simple security property) and 'no write down' (star property), prevents subjects from reading objects at a higher classification level and from writing to objects at a lower classification level, thereby preventing unauthorized disclosure of sensitive information.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Clark-Wilson
Why it's wrong here
Clark-Wilson is an integrity model based on transformation procedures and constrained data items.
Bell-LaPadula
Why this is correct
Correct. Bell-LaPadula is the confidentiality model with no read up and no write down.
Related concept
Read the scenario before looking for a memorised answer.
Biba
Why it's wrong here
Biba is an integrity model that enforces 'no read down' and 'no write up'.
Brewer-Nash
Why it's wrong here
Brewer-Nash (Chinese Wall) is a confidentiality model that prevents conflict of interest.
Common exam traps
The trap here is that candidates often confuse the Biba model's 'no read down, no write up' integrity rules with Bell-LaPadula's confidentiality rules, leading them to select Biba when the question specifically describes 'no read up, no write down'.
Detailed technical explanation
Under the hood, Bell-LaPadula uses a lattice of security levels (e.g., Unclassified, Confidential, Secret, Top Secret) and categories (e.g., NATO, Nuclear). The 'no read up' rule prevents a subject at Secret from reading a Top Secret object, while 'no write down' prevents a subject at Secret from writing to an Unclassified object, which could leak data. A subtle behavior is that the model does not prevent 'write up' (a subject writing to a higher level), which can be exploited in covert channel attacks if not combined with integrity models like Biba.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
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FAQ
Security Architecture and Engineering — This question tests Security Architecture and Engineering — Read the scenario before looking for a memorised answer..
The correct answer is: Bell-LaPadula — The Bell-LaPadula model is a formal state machine model for enforcing access control in government and military systems. Its core rule, 'no read up' (simple security property) and 'no write down' (star property), prevents subjects from reading objects at a higher classification level and from writing to objects at a lower classification level, thereby preventing unauthorized disclosure of sensitive information.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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.
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