CISSP Security Architecture and Engineering Practice Question
This CISSP practice question tests your understanding of security architecture and engineering. 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.
A security architect is considering secure design principles. Which two principles are essential for a defense-in-depth strategy? (Select TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Layered security
Layered security (defense in depth) is essential because it implements multiple, overlapping security controls so that if one layer fails, another layer continues to provide protection. This principle ensures that no single vulnerability can compromise the entire system, which is the core of a defense-in-depth strategy. Least privilege is equally essential because it restricts users and processes to only the minimum permissions necessary, limiting the blast radius of any breach and preventing lateral movement across layers.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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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Single point of failure
Why it's wrong here
Single point of failure is to be avoided, not essential.
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Layered security
Why this is correct
Correct. Multiple layers of defense are core to defense-in-depth.
Related concept
Read the scenario before looking for a memorised answer.
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Open design
Why it's wrong here
Open design is a principle but not essential for defense-in-depth.
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Fail safe
Why it's wrong here
Fail safe is important but not always considered essential for defense-in-depth; layered security and least privilege are more fundamental.
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Least privilege
Why this is correct
Correct. Limiting privileges reduces the impact of a breach.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'fail safe' or 'open design' as core to defense in depth, but the exam specifically tests that defense in depth is defined by layered security and least privilege, not by fail-safe mechanisms or design transparency.
Detailed technical explanation
How to think about this question
Defense in depth leverages multiple independent controls such as network firewalls (e.g., iptables rules), host-based intrusion detection (e.g., Snort), application-level input validation, and encryption at rest (e.g., AES-256) and in transit (e.g., TLS 1.3). Least privilege is enforced via operating system mechanisms like discretionary access control (DAC) lists or mandatory access control (MAC) with SELinux policies, ensuring that even if an attacker compromises a low-privilege account, they cannot escalate to root or access sensitive resources. In a real-world scenario, a web server with both a WAF and strict file permissions (e.g., 644 for static files, 700 for configuration) demonstrates how these principles combine to prevent a single SQL injection from leading to full system compromise.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Security Architecture and Engineering — This question tests Security Architecture and Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Layered security — Layered security (defense in depth) is essential because it implements multiple, overlapping security controls so that if one layer fails, another layer continues to provide protection. This principle ensures that no single vulnerability can compromise the entire system, which is the core of a defense-in-depth strategy. Least privilege is equally essential because it restricts users and processes to only the minimum permissions necessary, limiting the blast radius of any breach and preventing lateral movement across layers.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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