What is a firewall?

What is a firewall?

A firewall is a software program or piece of hardware that helps screen out hackers, viruses, and worms that try to reach your computer over the Internet.

NOTE: A firewall is essential, but you also need antivirus software and antispyware software.
 

If you use a computer at home, the most effective and important first step you can take to help protect your computer is to turn on a firewall.

• If you have more than one computer connected in the home, or if you have a small-office network, it is important to protect every computer. You should have a hardware firewall (such as a router) to protect your network, but you should also use a software firewall on each computer to help prevent the spread of a virus in your network if one of the computers becomes infected.

• If your computer is part of a business, school, or other organizational network, you should follow the policy established by the network administrator. In some cases, network administrators may configure all computers on the network so that you cannot turn on the firewall while your computer is connected to the network. In those cases, you should ask your network administrator for guidance on whether you need a firewall on your computer.
  

Microsoft Corporation