Quick Answer
The correct answer is least privilege, and defense in depth is the other fundamental security principle tested here. Least privilege ensures users and systems are granted only the minimum permissions necessary to perform their tasks, reducing the attack surface and limiting potential damage from compromised accounts. Defense in depth complements this by implementing multiple layers of security controls—such as firewalls, intrusion detection systems, encryption, and access controls—so that if one layer fails, others continue to provide protection, preventing a single point of failure from compromising the entire system. On the ISC2 Certified in Cybersecurity CC exam, these principles appear in scenario-based questions where you must identify which strategy best prevents unauthorized access or data breaches; a common trap is confusing defense in depth with simple redundancy or mistaking least privilege for role-based access control alone. Remember the mnemonic “Layers and Limits”: defense in depth is about layers of protection, while least privilege is about limiting permissions to the bare minimum.
This CC practice question tests your understanding of security principles. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 TWO of the following are fundamental security principles? (Select TWO.)
Fail-open
Why wrong: Fail-open is not a security principle; it's an insecure failure mode.
Need to share
Why wrong: Need to share is not a principle; 'need to know' is.
Defense in depth
Correct. Defense in depth is a key principle.
Least privilege
Correct. Least privilege is a core principle.
Complexity
Why wrong: Complexity is generally avoided, not a principle.
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
Defense in depth is a fundamental security principle that implements multiple layers of security controls (e.g., firewalls, IDS/IPS, encryption, access controls) so that if one layer fails, others still provide protection. This layered approach ensures no single point of failure can compromise the entire system, aligning with the CC exam's emphasis on holistic security strategies.
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.
Fail-open
Why it's wrong here
Fail-open is not a security principle; it's an insecure failure mode.
Need to share
Why it's wrong here
Need to share is not a principle; 'need to know' is.
Defense in depth
Why this is correct
Correct. Defense in depth is a key principle.
Related concept
Read the scenario before looking for a memorised answer.
Least privilege
Why this is correct
Correct. Least privilege is a core principle.
Related concept
Read the scenario before looking for a memorised answer.
Complexity
Why it's wrong here
Complexity is generally avoided, not a principle.
Common exam traps
ISC2 often tests the distinction between security principles (like defense in depth and least privilege) and design concepts (like fail-open or complexity), so candidates mistakenly select 'fail-open' because it sounds security-related, but it actually reduces security in a failure scenario.
Detailed technical explanation
Defense in depth is often implemented using overlapping controls such as network segmentation (VLANs, ACLs), host-based firewalls (e.g., Windows Defender Firewall with IPsec rules), and application-layer validation (e.g., input sanitization against SQL injection). In practice, a web server might be protected by a WAF, a network firewall, and OS-level file permissions, ensuring that even if the WAF is bypassed, the OS permissions block unauthorized access. This principle is codified in NIST SP 800-53 and ISO 27001 as a core security architecture requirement.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
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FAQ
Security Principles — This question tests Security Principles — Read the scenario before looking for a memorised answer..
The correct answer is: Defense in depth — Defense in depth is a fundamental security principle that implements multiple layers of security controls (e.g., firewalls, IDS/IPS, encryption, access controls) so that if one layer fails, others still provide protection. This layered approach ensures no single point of failure can compromise the entire system, aligning with the CC exam's emphasis on holistic security strategies.
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 30, 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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