Description

A firewall in a computer network provides security at the perimeter by monitoring incoming and outgoing data packets in network traffic for malware and anomalies. A firewall filters traffic as it attempts to enter and exit your network as opposed to antivirus software that scans devices and storage systems on the network for threats that have penetrated your defenses.

A firewall is designed to follow a predefined set of security rules to determine what to allow on your network and what to block.

Depending on where it is deployed and its purpose, a firewall can be delivered as a hardware appliance, as software, or software as a service (SaaS). There are five main types of firewalls depending upon their operational method:

1. stateless or packet filtering firewall
2. stateful inspection firewall
3. circuit-level gateway
4. application-level gateway
5. next-generation firewall (NGFW)

The following sections cover the different types of firewalls based on operational method and delivery method.