Firewall types (continued)
Application level gateways: also called proxies, are application specific. An application level gateway that is configured to be a web proxy will not allow any ftp, gopher, telnet or other traffic through. They offer a high level of security, but have a significant impact on network performance.
- Stateful Multilayer Firewalls: combine aspects of the other three types of firewalls. They filter packets at the network layer and evaluate contents of packets at the application layer. They allow direct connection between client and host, and they rely on algorithms to recognize and process application layer data instead of running application specific proxies.