Which of the following firewalls monitors the state of every connection on the…

Correct answer: Dynamic Packet Filtering Firewall.

A dynamic packet filtering firewall (also called a stateful inspection firewall) maintains a state table that tracks every active connection — for example, TCP streams, UDP sessions and ICMP exchanges. When a packet arrives, the firewall checks it against this state table and allows it only if it belongs to a valid, established connection. Because decisions are made using the full context of the connection rather than each packet in isolation, it offers much stronger security than simple packet filtering.

In contrast, a static packet filtering firewall is stateless: it examines each packet independently against fixed rules (source/destination IP, port, protocol) and keeps no memory of previous packets or connection state. Proxy firewalls and application gateways work at the application layer by inspecting and relaying content, while a circuit-level gateway works at the session layer by validating TCP handshakes. None of these is defined by 'monitoring the state of every connection', which is precisely the hallmark of dynamic (stateful) packet filtering.