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