An Overview of Firewall Security Technologies
Many companies engage in marketing hype to try to prove that their technology is better. Despite the hype, all firewall security technology can be broken down into three basic types: packet filtering (stateful or otherwise), application layer gateways, and Stateful Inspection.
Packet filters screen all network traffic at the network and transport layer of the TCP/IP packet. This means they look at source and destination IP addresses, protocol number, and, in the case of TCP and UDP, source and destination port numbers. Packet filtering is built into routers as well as some UNIX kernels. Usually, when site administrators start thinking about network security, they start with packet filtering ...