Which firewall type is capable of applying packet filtering at the network layer and evaluating application-layer contents for allowed sessions?

• A. Packet Filtering Firewall
• B. Stateful Multilayer Inspection Firewalls
• C. NAT
• D. Application-Level Proxy

Answer: (B)

This type of firewall combines stateful tracking with deep inspection across multiple protocol layers, allowing decisions based on both how a connection starts and what its actual data contains. It keeps a state table for each session and can filter by network-layer attributes (IP addresses, ports) while also examining application-layer contents to ensure sessions conform to allowed protocols and behaviors. That combination—network-layer filtering plus application-layer content evaluation—best fits the description.

A packet-filtering firewall looks only at header information and doesn’t inspect payload or track session state deeply. NAT focuses on translating addresses rather than inspecting traffic. An application-level proxy handles specific application protocols at the application layer but typically doesn’t provide broad network-layer filtering with stateful, multi-layer inspection across all sessions.