The answer is an Intrusion Prevention System (IPS). An IPS is the most appropriate device because it operates inline on the network, performing deep packet inspection up to Layer 7 to analyze the full payload of traffic, and can automatically block specific application-layer attacks like SQL injection or cross-site scripting in real time. On the CompTIA Network+ N10-009 exam, this question tests your ability to distinguish between active and passive security controls; a common trap is choosing an Intrusion Detection System (IDS), which can only alert on threats but cannot block them. Remember that an IPS sits inline and takes action, while an IDS only monitors out-of-band. For a quick memory tip, think of the “P” in IPS as standing for “Prevent” or “Police”—it actively stops the attack, not just reports it.
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?
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.
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.
✓
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.
✗
VPN concentrator
Why it's wrong here
A VPN concentrator handles encryption and tunneling for remote access, not attack detection or deep packet inspection.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
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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Question Discussion
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