Surfing Safe: Firewalls

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Introduction

The internet is a big place. Really big. And just like in the real world, not everyone plays by the rules. News stories about hackers and virus writers causing havoc with computer systems around the globe are commonplace, and this trend is not set to end any time soon.

We often hear stories of major companies that have fallen victim to the latest super-viruses, having their computer systems paralysed for hours or even days at a time, losing millions of dollars in the process. Internet hackers hold regular competitions to see how many websites they can deface or bring down in a given time. The internet is not always a friendly place, and without some basic forms of protection, anyone that connects to the internet can be at risk.

Why Firewalls Are A Good Idea

A typical PC running Microsoft Windows has many programs and services running 'in the background' - you don't see them, but they are there. Some of these allow you to transfer files between computers, others take care of printing, and others allow you to send and receive pop-up messages. Many of these services can accept requests from other computers, including those that are on the internet.

The problem is that it is not always desirable to have so many of these services being made available to the internet. For instance, someone could connect to your computer and start copying files from your hard-drive, including personal emails, or confidential documents. They may also be able to send advertisements directly to your screen in the form of text messages.

To make matters worse, not all of these services were written entirely perfectly. Some of them have 'bugs', or imperfections that can allow an attacker to take control of your computer simply by sending the right set of instructions, causing them to fail. The Blaster worm was one such internet threat that used this technique.

Firewalls, even the most basic ones, can prevent many of these problems.

What Firewalls Do

A Firewall is a piece of hardware or software that sits between these services on your computer and the internet. Its purpose in life is to restrict others on the internet from accessing these services. Firewalls can be configured to allow certain requests to come through to your computer, while rejecting others that you don't want. In an ideal situation, you would want to block absolutely everything and everyone from trying to connect to your computer, but this is not always possible depending on your circumstances.

If you run a business, you may need some services to be available to the internet. For instance, if you have your own email server, you need to allow other computers to send emails to your server in order for you to receive them. If you run your own web server, you need to allow other computers on the internet to browse your web pages, and so on.

Still, if you can block the vast majority of the 'unwanted' connections to your computer, you are a lot better off than having a computer that is completely exposed to the internet. A properly configured firewall can stop the Blaster worm - and others - from infecting your PC without interfering with your regular web browsing or sending and receiving of email.

What They Don't Do

Firewalls will not protect you from many viruses. Most viruses these days spread through email, and in general you would not set a firewall to block email traffic going to or from your computer.

When Are You At Risk?

As soon as you connect to the internet, whether by dial-up modem or through Broadband connections such as ADSL or Cable, you are a potential target for internet nasties to come knocking at your door. The longer you are connected to the internet, the higher your risk. Many internet worms such as Blaster, and Code Red simply scan random addresses on the internet for potential victims until they find one.

It doesn't matter to them whether you are a major company or a home user - the fact that you are connected to the internet means that it is most likely only a matter of time before one of these tries to get into your computer. For broadband users this is a particular problem, as these are generally 'always on' connections, and your computer may be left switched on for long periods of time, leaving them exposed.

Stopping The Bad Guys

If you use Windows XP, you can turn on the Internet Connection Firewall, which does an acceptable job of preventing access to your computer. If you run older versions of Windows, or want better protection, you can look at purchasing software firewall programs which will protect individual computers.

If you have several computers that all need access to the internet, you can purchase purpose-built firewall devices that you can plug your computers into, and effectively share the one internet connection securely between as many computers as you require. If you have an old computer and a bit of knowledge about networking, you can even configure this as a firewall quite cheaply using software that is available for free on the internet.

Traditionally, hardware firewalls have been favoured over software alternatives as the most secure, because they are less likely to suffer from security flaws that may be present within the operating system of your computer. These days, Windows and other well-known operating systems generally have quite robust network protocols, so software solutions are by no means unreliable or particularly less secure than hardware firewalls.

In Summary:

• Firewalls protect your computer from many internet threats by blocking others from accessing your computer.
• Firewalls won't always protect you from viruses, particularly those transmitted through email.
• If you use a Broadband internet connection without a firewall, you are at a much higher risk of internet attacks.
• A well configured firewall will protect your computer from many threats without interfering with your normal web browsing or email transfer.
• Firewalls are not the be-all and end-all of internet security, but they are a very effective first-line of defence.