This CS0-003 practice question tests your understanding of security operations. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 best practices for securing a network firewall configuration? (Choose two.)
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement a default deny rule for inbound and outbound traffic
A default deny rule for inbound and outbound traffic ensures that only explicitly permitted traffic is allowed, which is the foundation of a secure firewall configuration. This approach aligns with the principle of least privilege and prevents unauthorized access or data exfiltration by blocking all traffic that is not specifically required. Without a default deny rule, any misconfiguration or unanticipated traffic could bypass security controls.
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.
✓
Implement a default deny rule for inbound and outbound traffic
Why this is correct
Ensures only explicitly permitted traffic passes.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✓
Apply least privilege access by restricting ports and IP addresses
Why this is correct
Limits attack surface.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable continuous monitoring of firewall logs
Why it's wrong here
Important practice but not a configuration best practice.
✗
Allow all traffic by default and block specific threats
Why it's wrong here
Violates security best practice of default deny.
✗
Use default vendor passwords for initial access
Why it's wrong here
Default passwords are insecure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between operational practices (like log monitoring) and configuration best practices, leading candidates to mistakenly select continuous monitoring as a configuration control rather than a detection control.
Detailed technical explanation
How to think about this question
In a stateful firewall, a default deny rule is typically implemented as an implicit deny at the end of the access control list (ACL), meaning any packet that does not match a permit statement is dropped. For example, in Cisco IOS, the 'deny ip any any' statement at the end of an ACL enforces this behavior, and the firewall maintains session state to allow return traffic only for established connections. In real-world scenarios, a default deny rule prevents lateral movement in a segmented network by blocking all inter-VLAN traffic unless explicitly permitted via security zone policies.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CS0-003 question in full detail.
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement a default deny rule for inbound and outbound traffic — A default deny rule for inbound and outbound traffic ensures that only explicitly permitted traffic is allowed, which is the foundation of a secure firewall configuration. This approach aligns with the principle of least privilege and prevents unauthorized access or data exfiltration by blocking all traffic that is not specifically required. Without a default deny rule, any misconfiguration or unanticipated traffic could bypass security controls.
What should I do if I get this CS0-003 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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