Definition[edit | edit source]
A packet filter firewall is a routing device that include access control functionality for system addresses and communication sessions. The access control functionality of a packet filter firewall is governed by a set of rules that allows or blocks network packets based on a number of their characteristics, including the source and destination addresses, the network protocol, and the source and destination port numbers.
Overview[edit | edit source]
Packet filter firewalls are usually placed at the outermost boundary with an untrusted network, and they form the first line of defense. An example of a packet filter firewall is a network router that employs filter rules to screen network traffic.