Use a firewall as a barrier between the public internet and your private computer or network and block threats including some malware and 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.
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.
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. It's like wearing a seatbelt in a car: it's a good idea but it won't guarantee your safety if you crash.
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: (part of Microsoft Windows XP Service Pack 2) 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.
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 a software firewall.
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 should be your first priority.
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