easyMultiple ChoiceObjective-mapped
ISC2 CC Fail-safe defaults / Default deny Practice Question
Network Topology
The exhibit shows the current iptables rules. Which security principle is most clearly enforced by the default policy?
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
✓
Fail-safe defaults
The default policy is DROP on the INPUT chain, meaning any traffic not explicitly allowed is denied. This enforces the 'fail-safe defaults' principle (also known as default deny), which dictates that access should be denied unless explicitly permitted. This is correct because it ensures that any unintended or unauthorized traffic is blocked by default. In contrast, least privilege (Option D) focuses on granting minimal necessary permissions to users, separation of duties (Option C) involves dividing responsibilities, and defense in depth (Option B) refers to multiple layers of security controls—none of which are directly demonstrated by the default policy alone. Therefore, the correct answer is A.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Fail-safe defaults
Why this is correct
The default drop policy ensures that any unapproved traffic is blocked, which is a fail-safe default.
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Defense in depth
Why it's wrong here
Defense in depth would require multiple layers; only one is shown.
- ✗
Separation of duties
Why it's wrong here
Separation of duties is about dividing tasks, not firewall rules.
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Least privilege
Why it's wrong here
While related, least privilege focuses on granting minimal access, whereas the default deny policy is the foundation.
Visual reference
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Related to this question
Learn chapter
Introduction to Security Principles
Key term
Least privilege
Least privilege is a security principle that means giving users, systems, or programs only the minimum permissions they need to do their job and nothing more.
Key term
Defense in depth
Defense in depth is a cybersecurity strategy that uses multiple layers of security controls to protect information and systems, so if one layer fails, another layer is already in place to stop the attack.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.