Firewall Types

A firewall is a wall or partition that is designed to prevent fire from spreading from one part of a building to another. In computer networking, a firewall is designed to control, or filter, which communications are allowed in and which are allowed out of a device or network, as shown in the figure. A firewall can be installed on a single computer with the purpose of protecting that one computer (host-based firewall), or it can be a stand-alone network device that protects an entire network of computers and all of the host devices on that network (network-based firewall).

Over the years, as computer and network attacks have become more sophisticated, new types of firewalls have been developed which serve different purposes in protecting a network. Here is a list of common firewall types:

Network Layer Firewall – filtering based on source and destination IP addresses

Transport Layer Firewall – filtering based on source and destination data ports, and filtering based on connection states

Application Layer Firewall – filtering based on application, program or service

Context Aware Application Firewall – filtering based on the user, device, role, application type, and threat profile

Proxy Server – filtering of web content requests like URL, domain, media, etc.

Reverse Proxy Server – placed in front of web servers, reverse proxy servers protect, hide, offload, and distribute access to web servers

Network Address Translation (NAT) Firewall – hides or masquerades the private addresses of network hosts

Host-based Firewall – filtering of ports and system service calls on a single computer operating system