CISSP Communication and Network Security Practice Question
Which type of firewall operates at Layer 7 and can inspect application payloads, such as blocking specific SQL commands or HTTP methods?
⚠ Common exam trap
Test-takers frequently confuse 'stateful inspection' (Layer 4) with application-layer inspection, assuming stateful firewalls can inspect payloads, but they only track session state, not application content.
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.
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.
- ✗
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.
Go deeper
Related to this question
Learn chapter
Security Governance and Principles
Key term
OSI model
The OSI model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers, from physical hardware to application software.
Key term
Firewall
A firewall is a network security system that monitors and controls incoming and outgoing traffic based on predetermined security rules to protect trusted internal networks from untrusted external networks.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.