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Use a firewall

Firewalls keep out some viruses and hackers

A firewall acts as a barrier between the public internet and your private computer or network and blocks threats including some viruses.

Why install a firewall?

A firewall protects you against a number of different online threats:

• Hackers breaking into your computer.
• Some viruses, called “worms,” that spread from computer to computer over the internet.
• Some firewalls block outgoing traffic that might originate from a virus infection.

What a firewall does

Because the internet is a public network, any connected computer can find and connect to any other connected computer. A firewall is a barrier between the public internet and your private computer system. Think of it as a really paranoid bouncer who stops anyone coming into your computer if they’re not on the guest list.

What a firewall does NOT do

A firewall isn’t sufficient on its own to guarantee security, but it is the first line of defence. You also need to take the other protective steps outlined on this website. However, a firewall provides limited or no protection:

• If you give permission for other computers to connect to yours.
• If it is switched off, disabled or contains many exceptions or open ports.
• Against most viruses.
• Against spam.
• Against spyware installations.
• Against any kind of fraud or criminal activity online.
• If you or a virus has created a back door through the firewall.
• If a hacker has the password for the firewall.
• Against people with physical access to your computer or network.
• Against malicious traffic that does not travel through it, for example via a poorly configured wireless network.
• Against attacks after a network has been compromised.
• Against traffic that appears to be legitimate.

None of these things give a reason NOT to install a firewall, however. The point is that a firewall on its own is not enough for complete security.

It is safest to assume that your internet service provider does NOT provide any kind of firewall and make sure you have the right software to protect yourself.

Types of firewall

Desktop firewall

A desktop firewall is installed on each computer that is connected to the internet and monitors (and blocks, where necessary) internet traffic. They are also sometimes known as ‘software firewalls.’ 

Windows Firewall is a basic firewall. You can replace it with a more sophisticated commercial desktop firewall or supplement it with a hardware firewall if you wish.

The benefits of a desktop firewall are: 

• Windows Firewall is free and included with Windows Vista and Windows XP (with the latest updates)
• Free software firewalls are also available for older systems in private use.
• Commercial desktop firewalls often integrate well with other security products like virus scanners.
• Easy to set up – no wiring or extra hardware.
• If you use a laptop, a desktop firewall will protect you wherever you connect to the internet.

We recommend that every computer should have a software firewall installed.

Hardware firewall

Hardware firewalls are often built into broadband internet routers. If several computers share an internet connection, a hardware firewall will protect all of them. Most router manufacturers offer devices with firewalls.

Although they are getting easier to use, configuring a hardware firewall is often trickier than configuring asoftware firewall. Most internet routers and firewalls have a password that lets you control them from your computer. It's a good idea to change that password so that it is not the default one.

There is usually little price difference between a router that includes a firewall and one without and so it pays to get the extra protection if you have a choice.You can have hardware and desktop firewalls and having both may give a small margin of extra security. However, a desktop firewall on each computer is your first priority.

Commercial firewall

Commercial firewalls operate in the same way as Windows Firewall but generally give you extra protection, more control over how the firewall works and more information about how to configure it. Most security software companies sell a firewall as a standalone software package or as part of a security suite that includes other protection such as a virus scanner. In addition, the basic version of Zone Alarm is free for personal use. For more choices, see the DMOZ list of personal firewalls.

How to install a desktop firewall

Your choice of desktop firewall depends on whether or not you are running Windows XP or Vista and whether or not you want to buy a commercial firewall.

• Windows Vista. You can make sure that your firewall is operational by opening the Security Centre in the Control Panel . A green light and the word ‘on’ should appear next to 'Firewall'.
• Windows XP. You can check that you have Microsoft Firewall installed and operational by checking the Security Centre in the Control Panel. A green light and the word ‘on’ should appear next to 'Firewall'. If there is no Security Centre, you need to update your operating system with the latest service pack. See Get the latest Windows updates for more information.
• Windows 95, 98, ME, 2000. See: Using older computers online safely.

How to test if your firewall is working

There are a couple of online sites that you can use to see if your firewall is protecting your computer:

• Symantec Security Check.
• ShieldsUP! (follow the links for ‘Shields Up’).  This site requires a little more technical knowledge to use properly.

How to configure a firewall

Most desktop firewalls require some training before they are fully configured. This is because they need to learn what programs you use and which ones connect to the internet. Windows Firewall pops up warnings when a program tries to connect to the internet for the first time. Other desktop firewalls work in a similar way but the information they give varies from product to product. The key thing is to pay attention to these messages and make sure that you only allow legitimate connections.