A firewall is a system designed to prevent unauthorized access to or from a private Network, some of the functionalities of firewall are, packet filtering and as a Proxy Server. It controls inbound and outbound traffic based on a set of rules, based on policies that inspect which ordered quads are allowed from which direction.
Can do other protocol verification to drop malicious or badly-formed traffic.
Stateful Firewall
Compares packets to the Connection Table first to automatically allow return traffic Operates on Whitelist
Connection Table
Records state on connections Stores ordered quads