Hardware Firewalls
Hardware firewalls can be purchased as a stand-alone product but more recently hardware firewalls are typically found in most broadband routers, and should be considered an important part of your system and network set-up, especially for anyone on a broadband connection. Hardware firewalls can be effective with little to no configuration, and they are able to protect every machine on a local network. A hardware firewall uses packet filtering to examine the header of a packet to determine its source and destination. This information is usually compared to a set of predefined or user-created rules through a configuration user interface that determine whether the packet is to be forwarded or dropped.

A computer user with general computer knowledge can plug in a firewall, adjust a few settings and have it work. To ensure that your firewall is configured for optimal security and protection however, consumers will no doubt need to learn the specific features of their hardware firewall, how to enable them, and most importantly, how to test the firewall to ensure it's doing its' job of protecting your network.

Software Firewalls
For individual home users, the most popular firewall choice is a software firewall. Software firewalls are installed on your computer (like any software) and you can customize it; allowing you some control over its function and protection features. A software firewall will protect your computer from outside attempts to control or gain access to your computer, and depending on your choice of software firewall, it could also provide protection against the most common Trojan programs or e-mail worms. Many software firewalls have user defined controls for setting up safe file and printer sharing and to block unsafe applications from running on your system. Additionally, software firewalls sometimes incorporate many privacy controls, web filtering and more. The downside to software firewalls is that they will only protect the computer they are installed on, not a network, so each computer will need to have a software firewall installed on it.

Routers as Firewalls

Routers sort data packets from the Internet and direct them to one or more computers or peripherals on local networks. They assign a unique local address to each connected unit, but all external Internet traffic seems to come and go from the router's single address. That prevents a simple attack on the PCs behind the router, but it's possible to bypass simple address translation devices.

Most current routers include real firewalls that block unauthorized data packets flowing in or out of the network. Most of them operate as simple packet filters, which provides a weak hardware firewall.

Good firewalls, the hardware and the software kind, use "Stateful Packet Inspection" (SPI) which examines the content of packets, not just packet addresses and ports, to block or permit packet transfer.