- A
Stateless packet filtering
Why wrong: Stateless firewalls filter each packet independently without considering connection state, making them unable to allow only return traffic.
- B
Stateful inspection
Stateful firewalls track the state of connections and permit inbound packets only if they match an existing session.
- C
Application proxy
Why wrong: Application proxy acts as an intermediary and can filter at the application layer, but it is not the primary technology for stateful traffic control.
- D
Packet filtering based on ACL only
Why wrong: ACL-based filtering is stateless and would require explicit rules for return traffic, which is less efficient.
Question 89 of 520
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network 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.
A security engineer is configuring a firewall to protect an internal network. The requirement is that internal users can initiate connections to the internet, but external hosts should not be able to initiate connections to internal hosts unless the internal host first requested the connection. Which firewall technology should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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
✓
Stateful inspection
Stateful inspection (B) tracks the state of active connections by maintaining a state table that records source/destination IPs, ports, and sequence numbers. It allows return traffic for connections initiated from the internal network while blocking unsolicited inbound traffic, which directly matches the requirement that external hosts cannot initiate connections unless the internal host requested them first.
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.
- ✗
Stateless packet filtering
Why it's wrong here
Stateless firewalls filter each packet independently without considering connection state, making them unable to allow only return traffic.
When this WOULD be correct
A question that asks for a simple, low-overhead firewall technology to filter traffic based solely on source/destination IP addresses and port numbers, without requiring state tracking or application-layer inspection, such as in a small network with minimal security requirements.
- ✓
Stateful inspection
Why this is correct
Stateful firewalls track the state of connections and permit inbound packets only if they match an existing session.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Application proxy
Why it's wrong here
Application proxy acts as an intermediary and can filter at the application layer, but it is not the primary technology for stateful traffic control.
- ✗
Packet filtering based on ACL only
Why it's wrong here
ACL-based filtering is stateless and would require explicit rules for return traffic, which is less efficient.
When this WOULD be correct
A question that asks for a simple, low-overhead method to allow or deny traffic based on source/destination IP addresses and ports, without requiring state tracking, such as in a small network with static rules and no need for connection awareness.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Stateful inspectionCorrect answer▾
Why this is correct
Stateful firewalls track the state of connections and permit inbound packets only if they match an existing session.
✗Stateless packet filteringWrong answer — click to see why▾
Why this is wrong here
Stateless packet filtering does not track connection state, so it cannot distinguish between packets belonging to a new connection initiated by an external host versus a response to an internal request. It cannot enforce the requirement that external hosts cannot initiate connections unless the internal host first requested it.
★ When this WOULD be the correct answer
A question that asks for a simple, low-overhead firewall technology to filter traffic based solely on source/destination IP addresses and port numbers, without requiring state tracking or application-layer inspection, such as in a small network with minimal security requirements.
Why candidates choose this
Candidates may confuse stateless filtering with stateful inspection, thinking that ACLs can be configured to allow return traffic, but they overlook that stateless firewalls cannot dynamically permit return traffic without explicit rules for every possible response.
✗Application proxyWrong answer — click to see why▾
Why this is wrong here
An application proxy operates at Layer 7 and can inspect application data, but it does not inherently track connection state to allow return traffic for outbound requests; stateful inspection is specifically designed for that purpose.
★ When this WOULD be the correct answer
A question requiring deep packet inspection, content filtering, or authentication at the application layer, such as 'Which firewall technology can block specific HTTP methods or inspect SQL queries?' would make application proxy the correct answer.
Why candidates choose this
Candidates may confuse proxy firewalls with stateful firewalls because both can handle outbound traffic, but they overlook that stateful inspection is the standard for tracking connection states to permit return traffic.
✗Packet filtering based on ACL onlyWrong answer — click to see why▾
Why this is wrong here
Packet filtering based on ACL only cannot track connection state, so it cannot distinguish between packets belonging to a new connection initiated by an external host and those belonging to an existing connection initiated by an internal host.
★ When this WOULD be the correct answer
A question that asks for a simple, low-overhead method to allow or deny traffic based on source/destination IP addresses and ports, without requiring state tracking, such as in a small network with static rules and no need for connection awareness.
Why candidates choose this
Candidates may think ACL-based filtering is sufficient for basic security and overlook the requirement for stateful tracking of connection initiation direction.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The N10-009 exam often tests the misconception that stateless packet filtering can handle return traffic by simply allowing inbound packets with a high source port, but without state tracking, it cannot verify that the packet actually belongs to an existing session, making stateful inspection the correct answer.
Detailed technical explanation
How to think about this question
Stateful inspection uses a state table that tracks TCP connection states (SYN, SYN-ACK, ACK) and UDP pseudo-state information (e.g., timeout-based session tracking). For TCP, it validates that inbound packets have the ACK flag set and match an existing session entry, dropping packets with only the SYN flag that are not part of a known handshake. In real-world deployments, this technology is implemented in firewalls like Cisco ASA or pfSense, where the state table size and timeout values (e.g., TCP idle timeout of 1 hour) directly impact performance and security.
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 administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Stateful inspection — Stateful inspection (B) tracks the state of active connections by maintaining a state table that records source/destination IPs, ports, and sequence numbers. It allows return traffic for connections initiated from the internal network while blocking unsolicited inbound traffic, which directly matches the requirement that external hosts cannot initiate connections unless the internal host requested them first.
What should I do if I get this N10-009 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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 11, 2026
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.
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