The built-in Windows Firewall does an acceptable job of protecting your computer against many backdoor communication attempts. Many applications that require a firewall exception to be added will do so automatically during installation (such as online games), but sometimes you will need to manually allow an application to have access to the internet.

First, load up the Control Panel by clicking on the Start Menu then Control Panel:

Then, click Security:

Now select Allow a program through Windows Firewall:

Once the Windows Firewall Settings box has loaded, click Add Program (if you wanted to allow a port, click Add Port):

You can add an application from the list (if it appears), or browse for the application you wish to allow manually:

Once you have selected the application, click OK. Once you have clicked OK for a second time in the Firewall Settings window you have successfully added a firewall exception.

A firewall is a bit of software (or hardware) that inspects network traffic and filters it based on a set of pre-defined rules. Generally speaking, this allows you to improve the security of your PC by blocking attempts to exploit flaws in Vista and other software.

Windows Vista does already come with a free firewall, but it is simple and only allows minimal customisation. To access the free firewall, go to Control Panel > Security > Windows Firewall. This should be enabled by default and provides a basic level of protection. If you also have a hardware router to connect to the internet, you will have an additional layer of protection which may be adequate enough.

However, if you want to see which programs on your PC are “dialing home” and passing on information then a more advanced firewall is required. The following free firewalls should give you this extra level of customisation:

Zome Alarm
Comodo
Sphinx
PC Tools Firewall

Zone Alarm is our preferred firewall, but other users may find Comodo or some of the other choices a better match.

If you want to test the security of your firewall setup, try the “Shields Up” link halfway down this page : http://www.grc.com/default.htm