Firewalls

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. 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 standalone network device that protects an entire network of computers and all of the host devices on that network (network-based firewall).

As computer and network attacks have become more sophisticated, new types of firewalls have been developed, which serve different purposes.

• Network layer firewall

This filters communications based on source and destination IP addresses.

• Transport layer firewall

Filters communications based on source and destination data ports, as well as connection states.

• Application layer firewall

Filters communications based on an application, program or service.

• Context aware layer firewall

Filters communications based on the user, device, role, application type and threat profile.

• Proxy server

Filters web content requests like URLs, domain names and media types.

• 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

This firewall hides or masquerades the private addresses of network hosts.

• Host-based-firewall

Filters ports and system service calls on a single computer operating system.