Quick Answer
The answer is defense in depth, as mutual authentication between every component before communication exemplifies layered security controls. Defense in depth relies on multiple, overlapping safeguards so that if one layer fails, another still protects the system; requiring each component to authenticate to every other component adds a distinct layer of verification that an attacker must bypass. On the ISC2 Certified in Cybersecurity CC exam, this question tests your ability to distinguish defense in depth from other principles like zero trust, least privilege, or separation of duties—a common trap is confusing the mutual authentication mechanism with the zero trust model, but remember that zero trust is an architectural approach, while defense in depth is the overarching principle of using multiple layers, of which mutual authentication is just one. A useful memory tip: think of a castle with a moat, walls, guards, and locked doors—each layer must be passed, just as every component must authenticate before communicating.
This CC practice question tests your understanding of security principles. 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.
A security professional is evaluating a system that uses a trust model where every component authenticates to each other before communicating. Which security principle does this model exemplify?
Least privilege
Why wrong: Least privilege limits access, not authentication.
Separation of duties
Why wrong: Separation of duties divides responsibilities.
Non-repudiation
Why wrong: Non-repudiation prevents denial.
Defense in depth
Mutual authentication adds a layer of security, exemplifying defense in depth.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Defense in depth
Correct: A - Defense in depth. While zero trust is a model, defense in depth is the principle of multiple layers; mutual authentication is one layer. Option B is wrong because least privilege is about access rights. Option C is wrong because separation of duties divides roles. Option D is wrong because non-repudiation prevents denial.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Least privilege
Why it's wrong here
Least privilege limits access, not authentication.
Separation of duties
Why it's wrong here
Separation of duties divides responsibilities.
Non-repudiation
Why it's wrong here
Non-repudiation prevents denial.
Defense in depth
Why this is correct
Mutual authentication adds a layer of security, exemplifying defense in depth.
Related concept
Authentication checks who the user is.
Common exam traps
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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. Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CC questions on access control and AAA configuration.
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FAQ
Security Principles — This question tests Security Principles — Authentication checks who the user is..
The correct answer is: Defense in depth — Correct: A - Defense in depth. While zero trust is a model, defense in depth is the principle of multiple layers; mutual authentication is one layer. Option B is wrong because least privilege is about access rights. Option C is wrong because separation of duties divides roles. Option D is wrong because non-repudiation prevents denial.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CC questions on access control and AAA configuration.
Authentication checks who the user is.
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Last reviewed: Jun 24, 2026
This CC 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 CC exam.
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