Which of the following types of firewall inspects only header information in network traffic?

Packet filter firewalls inspect only the header information of each packet - including IP addresses, TCP/UDP port numbers, and protocol type - without examining payload contents or tracking connection state. Each packet is evaluated independently against a static rule set. This makes them fast but limited, as they cannot detect attacks embedded in packet payloads.

Stateful inspection firewalls track the state of active connections in a state table, examining both header information and connection context - not just headers alone.

Circuit-level gateways operate at the session layer and monitor the TCP handshake to validate sessions, going beyond simple header inspection.

Application-level gateways (proxy firewalls) inspect the full packet payload at the application layer, performing deep content inspection far beyond header fields.