Certified Information Systems Security Professional (CISSP) — Question 123

At which layer of the Open Systems Interconnection (OSI) model does a circuit-level firewall operate?

Answer options

• A. Session layer
• B. Network layer
• C. Application layer
• D. Transport layer

Correct answer: A

Explanation

A circuit-level firewall functions at the Session layer of the OSI model, where it manages sessions and connections between devices. The Network layer is responsible for routing packets, the Application layer deals with end-user applications, and the Transport layer focuses on reliable data transport, making them unsuitable for circuit-level operations.