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CISSP Practice Question: Which THREE of the following are common security…
Which THREE of the following are common security design principles? (Select THREE.)
⚠ Common exam trap
Watch out — candidates often confuse 'single point of failure' as a design principle (it is a risk to be mitigated, not a principle) or mistakenly think 'security through obscurity' is a valid principle, when in fact the CISSP explicitly teaches that it is not a reliable security measure.
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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Open design
Open design (A) is a fundamental security principle stating that the security of a system should not depend on the secrecy of its implementation; instead, it relies on the strength of its cryptographic keys and algorithms. This principle is embodied in Kerckhoffs's principle, which asserts that a cryptosystem should remain secure even if everything about the system, except the key, is public knowledge. Open design allows for public scrutiny and peer review, which helps identify vulnerabilities and build trust in the system's security.
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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Open design
Why this is correct
The principle of open design dictates that the security of a mechanism should not depend on the secrecy of its design or implementation, but rather on the secrecy of its keys or other small, critical parameters. This approach, also known as Kerckhoffs's Principle, encourages public scrutiny and peer review, which are essential for identifying and rectifying vulnerabilities more effectively than relying on hidden details. It ensures that security is based on robust, verifiable controls, not on the hope that an attacker won't discover the system's inner workings.
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Least privilege
Why this is correct
Least privilege is a fundamental security principle requiring that a subject (user, process, or program) be granted only the minimum set of permissions or access rights necessary to perform its legitimate function. By limiting privileges, this principle significantly reduces the attack surface and minimizes the potential damage an attacker can inflict if a system component or user account is compromised. It effectively contains the impact of both accidental errors and malicious actions within a system.
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Single point of failure
Why it's wrong here
A single point of failure (SPOF) describes a component within a system that, if it fails or is compromised, will cause the entire system or a critical part of it to cease functioning. Far from being a security design principle, SPOFs represent a critical vulnerability that security architects actively strive to eliminate. Robust security design incorporates redundancy, fault tolerance, and distributed architectures to mitigate SPOFs, ensuring system availability and resilience against failures or attacks.
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Security through obscurity
Why it's wrong here
Security through obscurity is a flawed and unreliable approach where the perceived security of a system relies on keeping its design, implementation details, or vulnerabilities secret from potential attackers. This method is inherently weak because secrets can eventually be discovered, reverse-engineered, or leaked, rendering the system vulnerable without any actual robust protective mechanisms in place. It directly contradicts the principle of open design, as it prioritizes secrecy over verifiable security controls and public scrutiny.
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Economy of mechanism
Why this is correct
The principle of economy of mechanism states that security mechanisms should be as simple and small as possible, both in their design and implementation. Simplicity inherently reduces the likelihood of design flaws, implementation errors, and unintended side effects that could introduce exploitable vulnerabilities. A simpler system is easier to analyze, test, verify for correctness, and maintain securely over its lifecycle, thereby enhancing its overall trustworthiness.
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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.