- A
Stateful firewall
Why wrong: Stateful firewalls inspect up to Layer 4 (transport layer) and are not designed for deep application-layer inspection or attack blocking.
- B
Intrusion Prevention System (IPS)
IPS sits inline, performs deep packet inspection, and can actively block malicious traffic, including application-layer attacks.
- C
Proxy server
Why wrong: A proxy server can filter content and cache, but it is not primarily designed to block application-layer attacks; an IPS is more specialized for that role.
- D
VPN concentrator
Why wrong: A VPN concentrator handles encryption and tunneling for remote access, not attack detection or deep packet inspection.
Question 52 of 520
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 analyst needs to deploy a device that can perform deep packet inspection and block specific application-layer attacks in real time. Which of the following devices is MOST appropriate for this purpose?
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
✓
Intrusion Prevention System (IPS)
An Intrusion Prevention System (IPS) is designed to inspect traffic in real time, perform deep packet inspection (DPI) up to Layer 7, and automatically block malicious traffic, including application-layer attacks such as SQL injection or cross-site scripting. Unlike a passive IDS, an IPS sits inline and can drop or reset sessions based on signature or anomaly detection, making it the most appropriate device for this requirement.
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.
- ✗
Stateful firewall
Why it's wrong here
Stateful firewalls inspect up to Layer 4 (transport layer) and are not designed for deep application-layer inspection or attack blocking.
When this WOULD be correct
A stateful firewall would be correct when the requirement is to filter traffic based on connection state (e.g., allowing return traffic for established connections) and enforce basic access control policies without needing deep packet inspection or application-layer attack blocking.
- ✓
Intrusion Prevention System (IPS)
Why this is correct
IPS sits inline, performs deep packet inspection, and can actively block malicious traffic, including application-layer attacks.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Proxy server
Why it's wrong here
A proxy server can filter content and cache, but it is not primarily designed to block application-layer attacks; an IPS is more specialized for that role.
When this WOULD be correct
A proxy server would be correct if the question asked for a device that provides anonymous web browsing, content caching, or URL filtering to enforce acceptable use policies, without requiring real-time attack blocking.
- ✗
VPN concentrator
Why it's wrong here
A VPN concentrator handles encryption and tunneling for remote access, not attack detection or deep packet inspection.
When this WOULD be correct
A question asking for a device that securely connects remote users to a corporate network over the internet, with emphasis on encryption and tunnel management, would make a VPN concentrator the correct answer.
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.
✓Intrusion Prevention System (IPS)Correct answer▾
Why this is correct
IPS sits inline, performs deep packet inspection, and can actively block malicious traffic, including application-layer attacks.
✗Stateful firewallWrong answer — click to see why▾
Why this is wrong here
A stateful firewall tracks connection states and filters traffic based on state and port/protocol, but it does not perform deep packet inspection or block application-layer attacks in real time.
★ When this WOULD be the correct answer
A stateful firewall would be correct when the requirement is to filter traffic based on connection state (e.g., allowing return traffic for established connections) and enforce basic access control policies without needing deep packet inspection or application-layer attack blocking.
Why candidates choose this
Candidates may confuse stateful firewalls with next-generation firewalls (NGFWs) that do include DPI and application-layer filtering, or they may overestimate the capabilities of standard stateful firewalls.
✗Proxy serverWrong answer — click to see why▾
Why this is wrong here
A proxy server primarily acts as an intermediary for client requests, often caching content or filtering URLs, but it does not perform deep packet inspection or block application-layer attacks in real time like an IPS does.
★ When this WOULD be the correct answer
A proxy server would be correct if the question asked for a device that provides anonymous web browsing, content caching, or URL filtering to enforce acceptable use policies, without requiring real-time attack blocking.
Why candidates choose this
Candidates may confuse proxy servers with security devices because proxies can filter web traffic and block certain content, leading them to overestimate the proxy's ability to inspect and block application-layer attacks.
✗VPN concentratorWrong answer — click to see why▾
Why this is wrong here
A VPN concentrator is designed to manage VPN tunnels and encrypt/decrypt traffic, not to perform deep packet inspection or block application-layer attacks in real time.
★ When this WOULD be the correct answer
A question asking for a device that securely connects remote users to a corporate network over the internet, with emphasis on encryption and tunnel management, would make a VPN concentrator the correct answer.
Why candidates choose this
Candidates may confuse VPN concentrators with security devices because they handle encrypted traffic, but they lack the inspection and blocking capabilities required for application-layer attack prevention.
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 trap here is that candidates often confuse an IPS with a stateful firewall, assuming that stateful inspection includes deep packet inspection, but stateful firewalls only check packet headers and connection state, not application-layer payloads.
Detailed technical explanation
How to think about this question
An IPS uses a combination of signature-based detection (e.g., Snort rules), protocol anomaly detection, and behavioral analysis to identify threats; it can reassemble TCP streams and inspect payloads for patterns like SQL keywords or shellcode. In real-world deployments, an IPS must be carefully tuned to avoid false positives that could block legitimate traffic, and it often operates in 'inline' mode with fail-open or fail-close configurations to maintain availability or 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 practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
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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: Intrusion Prevention System (IPS) — An Intrusion Prevention System (IPS) is designed to inspect traffic in real time, perform deep packet inspection (DPI) up to Layer 7, and automatically block malicious traffic, including application-layer attacks such as SQL injection or cross-site scripting. Unlike a passive IDS, an IPS sits inline and can drop or reset sessions based on signature or anomaly detection, making it the most appropriate device for this requirement.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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