easyMultiple ChoiceObjective-mapped
CISSP Practice Question: Which security model focuses on preventing…
Which security model focuses on preventing unauthorized access by enforcing a 'no read up, no write down' rule?
⚠ Common exam trap
Many candidates 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'.
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
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.
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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Clark-Wilson
Why it's wrong here
The Clark-Wilson security model is an integrity model focused on preventing unauthorized modification of data and maintaining data consistency. It achieves this by enforcing well-formed transactions, where access to Constrained Data Items (CDIs) is strictly controlled through certified Transformation Procedures (TPs). Users are authorized to execute specific TPs, ensuring that data transitions from one valid state to another, thereby prioritizing data integrity over confidentiality.
- ✓
Bell-LaPadula
Why this is correct
The Bell-LaPadula security model is a foundational confidentiality model specifically designed to prevent unauthorized disclosure of information. It employs a mandatory access control mechanism based on security levels, enforcing two primary rules: the Simple Security Property ("no read up") and the *-Property ("no write down"). This ensures subjects can only access objects at or below their security clearance and cannot write information to a lower security level, effectively protecting classified data.
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Biba
Why it's wrong here
The Biba security model is an integrity-focused model designed to prevent data corruption and ensure the reliability and trustworthiness of information. It enforces two main rules based on integrity levels: the Simple Integrity Property ("no read down") and the *-Integrity Property ("no write up"). This means a subject cannot read data with a lower integrity level, nor can it write data to a higher integrity level, thereby protecting the integrity of information from untrusted sources.
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Brewer-Nash
Why it's wrong here
The Brewer-Nash security model, also known as the Chinese Wall model, is a confidentiality model designed to prevent conflicts of interest within an organization. It dynamically adjusts access permissions based on a user's past access history, ensuring that a user who has accessed information related to one company within a conflict-of-interest class cannot then access information related to a competing company in the same class. This model prevents individuals from gaining knowledge that could create an ethical or financial conflict.
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Related to this question
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Security Governance and Principles
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.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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