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, ports, and protocol flags - and apply rules to allow or deny traffic. They do not examine the data payload, maintain connection state, or understand application-layer protocols, making them the simplest and least context-aware firewall type.

Stateful inspection firewalls go beyond headers by tracking the state of active connections in a state table, allowing them to make context-aware decisions based on whether a packet belongs to an established session.

Circuit-level gateways operate at the session layer and validate TCP handshakes to verify that sessions are legitimate before allowing traffic, which involves more than just header inspection.

Application-level gateways (proxy firewalls) perform deep packet inspection at Layer 7, analyzing the full application payload and protocol behavior, which is far more than header-only inspection.