CISSP Security Architecture and Engineering Practice Question
An organization implements a security model where users can only read objects at or below their security clearance, and can only write to objects at or above their clearance. This model primarily ensures:
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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Confidentiality
The described model is the Bell-LaPadula model, which enforces confidentiality. In Bell-LaPadula, subjects can read objects at or below their security level (read down) and write to objects at or above their level (write up). This prevents unauthorized access to higher classified information, ensuring 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.
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Integrity
Why it's wrong here
While integrity is a critical security objective, the Bell-LaPadula model, which is implied by the 'no read up, no write down' rules, does not prioritize it. Instead, Bell-LaPadula focuses on preventing unauthorized disclosure of information, which is confidentiality. The Biba model, conversely, is specifically designed to maintain data integrity by preventing subjects from writing to higher integrity levels or reading from lower integrity levels, thereby protecting data from contamination.
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Confidentiality
Why this is correct
The Bell-LaPadula model is specifically designed to enforce confidentiality in multi-level security environments. It achieves this through two primary rules: the simple security property, which prevents subjects from reading objects at a higher classification level ('no read up'), and the *-property (star property), which prevents subjects from writing to objects at a lower classification level ('no write down'). These rules collectively ensure that sensitive information cannot flow downwards to less secure classifications, thereby preserving its secrecy.
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Accountability
Why it's wrong here
Accountability is the ability to trace actions back to an individual or entity, ensuring non-repudiation and responsibility for their activities. This is primarily achieved through robust auditing, logging, and monitoring mechanisms that record user activities and system events. Access control models like Bell-LaPadula define *what* actions are permissible based on security classifications, but they do not inherently provide the logging infrastructure necessary to establish accountability for those actions.
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Availability
Why it's wrong here
Availability ensures that authorized users can access information and resources when needed, without undue delay or interruption. This security principle is typically addressed through redundant systems, fault tolerance, disaster recovery planning, and protection against denial-of-service attacks. The Bell-LaPadula model, focused on preventing unauthorized information disclosure, does not directly contribute to the continuous operational state or resilience of a system, which are core tenets of availability.
Go deeper
Related to this question
Learn chapter
Security Governance and Principles
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
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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JA
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.