- A
Stateful inspection
Why wrong: Stateful firewalls track connection state but do not deeply inspect application payloads.
- B
Application proxy
Application proxies terminate the connection and re-establish it, inspecting the application data.
- C
Packet filter
Why wrong: Packet filters examine only headers (IP addresses, ports).
- D
Circuit-level gateway
Why wrong: Circuit-level gateways operate at Layer 5 (session) and do not inspect application data.
Question 932 of 1,000
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 type of firewall operates at Layer 7 and can inspect application payloads, such as blocking specific SQL commands or HTTP methods?
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
✓
Application proxy
An application proxy firewall (also known as an application-level gateway) operates at Layer 7 (Application Layer) of the OSI model. It can inspect the full application payload, allowing it to block specific SQL commands, HTTP methods (e.g., PUT, DELETE), or other application-layer content by terminating the connection and re-establishing it after deep inspection.
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 inspection
Why it's wrong here
Stateful firewalls track connection state but do not deeply inspect application payloads.
- ✓
Application proxy
Why this is correct
Application proxies terminate the connection and re-establish it, inspecting the application data.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Packet filter
Why it's wrong here
Packet filters examine only headers (IP addresses, ports).
- ✗
Circuit-level gateway
Why it's wrong here
Circuit-level gateways operate at Layer 5 (session) and do not inspect application data.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'stateful inspection' (Layer 4) with application-layer inspection, assuming stateful firewalls can inspect payloads, but they only track session state, not application content.
Detailed technical explanation
How to think about this question
Application proxy firewalls act as intermediaries, terminating the client connection and creating a new connection to the server, which allows full reassembly and inspection of application-layer protocols like HTTP, FTP, or SQL. For example, an application proxy can parse SQL queries to block 'DROP TABLE' commands or inspect HTTP headers to reject malicious methods like TRACE or CONNECT. This deep inspection introduces latency but provides granular control, often used in web application firewalls (WAFs) to mitigate SQL injection and cross-site scripting (XSS) attacks.
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.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
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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Communication and Network Security — study guide chapter
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FAQ
Questions learners often ask
What does this CISSP question test?
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Application proxy — An application proxy firewall (also known as an application-level gateway) operates at Layer 7 (Application Layer) of the OSI model. It can inspect the full application payload, allowing it to block specific SQL commands, HTTP methods (e.g., PUT, DELETE), or other application-layer content by terminating the connection and re-establishing it after deep inspection.
What should I do if I get this CISSP 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.
About these practice questions
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Last reviewed: Jul 4, 2026
This CISSP 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 CISSP exam.
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