Firewall Technologies
There are three firewall technologies:
■ Packet filtering—Inspects the incoming and outgoing packets and allows/denies traffic
based on source, destination, protocol, and service.
■ Proxy—Connections are initiated by the firewall on behalf of the requestor. Traffic does
not pass through a proxy-based firewall but rather is re-created by the firewall.
■ Stateful packet inspection—Stateful packet inspection firewalls, also know as stateful
packet filters, allow/deny traffic based on source, destination, and service while
maintaining a state table to keep track of existing connections. This ensures that inbound
connections are valid replies to outbound requests.