A Router is a networking device that directs the flow of data along networks. Routers are connected to at least two separate networks, commonly two LANs (Local Area Network) or WANs (Wide Area Network) or, as in your home network, your LAN and the Internet. Routers are also known as gateways, located where two or more networks connect, and are the critical device that keeps data flowing between the networks.

The routers we use in our home networks are sometimes referred to as “residential gateways” and are frequently used to connect to a broadband service over cable or DSL. These routers may also include an internal cable or DSL modem. Residential gateways typically provide firewall functionality through network address translation (NAT) and port address translation. Instead of directly presenting the IP addresses of local computers to the remote network, such a residential gateway makes multiple local computers appear to be a single computer. In terms of home network security, your router is the mask you wear, effectively hiding your real identity from the internet.

This article provides a very simplistic definition of a router. The router performs an amazing amount of work behind the scenes, and is the device that is most responsible for allowing the Internet to work at all.

Simply put, you are playing with fire if you aren’t using a firewall to protect your PC and home network from unauthorized access from outside your network.

The term “firewall” originally referred to a physical barricade against the potential spread of fire. In home computing terms, a firewall is a component of a computer or network that acts as a barrier between your home network or PC and the Internet. The firewall blocks unauthorized access while allowing authorized access to your systems. Firewalls can be hardware devices or based in software, both serving the same function.

Firewalls work by inspecting all traffic, both inbound and outbound, and deciding whether the traffic is denied or allowed passage based on a set of pre-established rules or policies. These rules and policies can work in one or more of several methods:

NAT – Network Address Translation
NAT is a method of connecting multiple computers to the Internet (or any other network) using one IP address. NAT allows one IP address, which is shown to the outside world, to refer to many IP addresses internally; one on each PC. NAT automatically provides firewall-style protection without any special set-up because it only allows connections that are originated on the inside network.

Packet Filter
Packet filtering blocks traffic based on a specific Web address (IP address) or type of application (e-mail, ftp, Web, etc.) .

SPI – Stateful Packet Inspection
SPI tracks the data to ensure that the inbound data were requested by the user.

Refer to your router’s user manual for instructions on how to set up your firewall. There are many online resources that discuss some of the more complex issues with firewalls, but for most home network users, the default settings will provide a very high level of security.

Windows comes with a built in software firewall that you can turn off if using a hardware firewall. Microsoft, however, recommends that you leave it on to provide protection if one of the PCs on your home network should become infected and start sending out malicious data.

• Information on the Windows firewall can be found here.