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ISC2 CC Practice Question: Is configuring a firewall to allow web traffic…
A security engineer is configuring a firewall to allow web traffic but block all other inbound connections. The firewall is set to deny all traffic by default and only allow specific ports. Which security principle is being applied?
⚠ Common exam trap
ISC2 often tests the distinction between 'default deny' (a firewall ACL posture) and 'least privilege' (a user/process access control model), causing candidates to confuse network-level traffic filtering with user-level permissions.
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
✓
Default deny
Default deny. The scenario describes a firewall configured to deny all traffic by default and then explicitly allow only specific ports (e.g., TCP 80/443 for web traffic). This directly implements the default deny security principle, where any traffic not explicitly permitted is blocked. This contrasts with a default allow posture, which would permit all traffic unless explicitly denied.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Default deny
Why this is correct
Correct. The firewall denies everything by default.
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Defense in depth
Why it's wrong here
Defense in depth is about multiple layers, not default deny.
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Fail-safe
Why it's wrong here
Fail-safe ensures system remains secure on failure, not default deny.
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Least privilege
Why it's wrong here
Least privilege applies to user permissions, not network traffic.
Go deeper
Related to this question
Learn chapter
Introduction to Security Principles
Key term
TCP
TCP is a connection-oriented transport layer protocol that ensures reliable, ordered, and error-checked delivery of data between applications over IP networks.
Key term
Firewall
A firewall is a network security system that monitors and controls incoming and outgoing traffic based on predetermined security rules to protect trusted internal networks from untrusted external networks.
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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.