What are the main technologies of firewalls?

The main technologies of firewall include network layer firewall, application layer firewall, packet filtering firewall and stateful inspection firewall. Detailed introduction: 1. Network layer firewall, which filters and controls network traffic based on network protocols and IP addresses; 2. Application layer firewall, performs in-depth detection and filtering of application layer protocols to provide more refined access control and security protection; 3. . Packet filtering firewall, which filters and controls network packets according to preset rules; 4. Stateful detection firewall, monitors and analyzes network connections, and decides whether to allow data packets to pass through based on the status of the connection.