Is your firewall up to the task?

While the internet is a mine of information and social interaction, it’s not all friendly faces. Indeed, there are those with an agenda of making mischief by infiltrating computers connected to the internet.

A first line of defence against these sneaks is a firewall: a set of technical tricks that help to prevent bad stuff getting into a PC and limit what goes out. Windows includes one and routers that connect many home PCs to the internet also include firewalls.

In this Back to Basics, we explain what a firewall is, how they work and how to make sure your PC is properly protected.

What is a firewall?
Any PC connected to the internet needs a firewall, which controls what’s allowed to come in and what’s allowed to leave it. It’s important to have a ‘gatekeeper’ like this to keep an eye on what’s going on for two reasons.

First, any broadband-connected computer is typically permanently connected to the internet. Second, each online PC has a unique electronic signature, called an Internet Protocol address (or IP address): without a firewall in place, this is like turning all the lights on and leaving the front door open.

A properly configured firewall stops this from happening and makes the computer effectively ‘invisible’, allowing you to enjoy what the online world has to offer.

A firewall isn’t the same as an anti-virus program. Rather, it works alongside these tools to ensure that the computer is protected from the most common threats.

Windows XP, Vista and 7 include a firewall, called Windows Firewall, which is enabled (ie, switched on with defences up) by default. Double-check yours like this: XP users should click Start, followed by Control Panel, then click the Switch to Classic View link before double-clicking the Windows Firewall icon: check the On radio button is selected.

Vista or Windows 7 users should click Start, followed by Control Panel, choose System and Security (or just Security for Vista), then find the Windows Firewall heading and click it (Vista), or click ‘Check firewall status’ (Windows 7).

How does a firewall work?
A firewall’s job is a difficult one, because there’s plenty of legitimate data that needs to be allowed in and out of an online computer. For example, when visiting a website, downloading a program or updating Windows, information and program data needs to be transferred to and from the internet for these processes to work.

A firewall must know the difference between legitimate ‘traffic’ like this and the potentially dangerous stuff.

Firewalls use rules or exceptions to work out which connections are good and which ones are bad. Most of the time this goes on behind the scenes, with no user interaction required.

To see how XP handles it, click Start, then Control Panel and double-click the Windows Firewall icon. When the dialogue box appears, click the Exceptions tab at the top to see the programs allowed to receive incoming connections – it’s likely to include things like anti-virus software and online file storage services, such as Dropbox.

Using Vista or Windows 7? Click Start, then Control Panel, followed by System and Security (or Security in Vista), and Windows Firewall. When the window appears, click the ‘Allow a program or feature through Windows Firewall’ link in the list on the left (Vista calls this ‘Allow a program through Windows Firewall’) to see the programs allowed to communicate through the firewall.

Most of the time, Windows takes care of these rules and exceptions automatically, but this is the place to come if you need to change something.

Is Windows Firewall enough?
For XP users, Windows Firewall is probably not enough, as it doesn’t block outward connections: so, if a piece of malware has found its way onto the PC, there’s nothing to stop it from doing its dirty work. We’d recommend downloading something like the free Comodo Firewall and installing that alongside the XP one.

Vista and Windows 7’s firewalls don’t suffer from the same problem. Even so, we’d advise also enabling the hardware firewall built into your router – the device used to connect to the internet. Hardware firewalls are designed to keep bad stuff out and also protect every computer and device connected to a home network.

Each router is different, but most are controlled from a web browser-based configuration screen. Find the address by checking the manual (for example, with BT Infinity Home Hub, type http://bthomehub.home into a web browser’s address or location bar; others use an IP address, such as http://192.168.1.1).

Sign into the router’s control panel with the username and password created when it was first set up. Next, consult the router’s help file to find the firewall settings: for a BT Home Hub, this is under Settings, then Advanced Settings, followed by Port Forwarding.

On our test model, the hardware firewall was set to allow outgoing connections and block all unsolicited incoming traffic. Clicking Supported Applications showed that it was automatically set up to handle a range of programs and games needing internet access to work properly.

Fighting fire
In general, Windows 7 and Vista users have little to worry about, as the built-in firewall does the job. But as explained, XP users are advised to install an alternative program. In all cases, it’s worth checking your defences occasionally to get on with using the internet without worry.