Which of the following types of firewalls provide the GREATEST degree of control against hacker intrusion?

A packet filtering router operates at the network and transport layers, inspecting only header information like IP addresses and port numbers, offering less granular control.

A circuit-level gateway operates at the session layer, monitoring the TCP handshake and session state but not the content of the data packets themselves.

An application-level gateway, also known as a proxy firewall, operates at the application layer (Layer 7) of the OSI model, allowing it to inspect the actual content and commands within application-specific traffic (e.g., HTTP, FTP). This deep packet inspection provides the highest level of granular control and protection by filtering based on protocol syntax and behavior, effectively proxying connections.

A screening router is essentially a packet filtering router, providing basic filtering based on IP addresses and port numbers, which is a lower level of control.