The correct answer is that the default deny rule is missing. This is a critical security issue because a firewall policy without an explicit deny all rule at the bottom violates the principle of least privilege; any traffic not matching an explicit permit may be implicitly allowed or handled unpredictably, depending on the firewall platform, creating a gap in network defenses. On the Systems Security Certified Practitioner SSCP exam, this concept tests your understanding of firewall policy structure and secure configuration, often appearing in scenario-based questions where a policy shows only permit statements. A common trap is assuming that a firewall automatically blocks unmatched traffic, but many platforms default to an implicit allow unless a deny all rule is explicitly set. Memory tip: think of a firewall policy like a bouncer’s list—without a final “no entry” rule, anyone not on the list might still get in.
SSCP Network and Communications Security Practice Question
This SSCP practice question tests your understanding of network and communications security. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The default deny rule is missing
The exhibit shows a firewall policy with explicit permit rules but no explicit deny all rule at the bottom. Without a default deny rule, any traffic not matching an explicit permit may be implicitly allowed or handled unpredictably depending on the firewall platform, violating the security principle of least privilege. A proper firewall policy must end with an explicit deny all to block all unauthorized traffic.
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.
✗
Web traffic is allowed from any source
Why it's wrong here
This is intended for public access.
✓
The default deny rule is missing
Why this is correct
Without a deny all, any unmatched traffic is allowed.
Related concept
Read the scenario before looking for a memorised answer.
✗
The firewall is allowing all traffic on port 443
Why it's wrong here
Only port 443 is allowed to the internal subnet.
✗
The destination network is too broad
Why it's wrong here
Broad destination can be acceptable; missing deny is the issue.
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the concept that a firewall policy without an explicit deny all rule at the bottom is inherently insecure, even if all other rules appear correct, because candidates may focus on specific rule content rather than the overall policy structure.
Detailed technical explanation
How to think about this question
In firewall policy design, the default deny rule (often implemented as 'deny ip any any' or 'deny all') ensures that any traffic not explicitly permitted is dropped, preventing policy gaps. Without this rule, some firewall implementations may implicitly allow traffic that matches no rule, or the policy may behave inconsistently across different vendors (e.g., Cisco ASA vs. iptables). In real-world audits, missing default deny is a common finding that can lead to data exfiltration or unauthorized access.
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 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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network and Communications Security — This question tests Network and Communications Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The default deny rule is missing — The exhibit shows a firewall policy with explicit permit rules but no explicit deny all rule at the bottom. Without a default deny rule, any traffic not matching an explicit permit may be implicitly allowed or handled unpredictably depending on the firewall platform, violating the security principle of least privilege. A proper firewall policy must end with an explicit deny all to block all unauthorized traffic.
What should I do if I get this SSCP 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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This SSCP 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 SSCP exam.
Question Discussion
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