Firewalls FAQ

A firewall is a piece of software or hardware that helps screen out hackers, viruses, and worms that try to reach your computer over the Internet. If you are a home user or small-business user, using a firewall is the most effective and important first step you can take to help protect your computer.

It is important to turn on your firewall and antivirus software before you connect to the Internet.

If your computer is not protected when you connect to the Internet, hackers can gain access to personal information on your computer. They can install code on your computer that destroys files or causes malfunctions. They can also use your computer to cause problems on other home and business computers connected to the Internet. A firewall helps to screen out many kinds of malicious Internet traffic before it reaches your computer.

Some firewalls can also help to prevent other people from using your computer to attack other computers without your knowledge. Using a firewall is important no matter how you connect to the Internet—with a dial-up modem, cable modem, or digital subscriber line (DSL or ADSL).

If you have Windows Vista or Windows XP Service Pack 2 (SP2) or higher running on your computer, you can check to see if your firewall is turned on through the Windows Security Center:

1. Click Start, and then click Control Panel.
2. Click Security Center, and then click Windows Firewall.

If you have Windows XP, but you don't have Service Pack 2 running on your computer, you can download it by visiting Microsoft Update. You can also take the following steps to make sure the firewall is turned on:

1. Click Start, and then click Control Panel.
2. Click Network and Internet Connections, and then click Network Connections.
   Tip: If the Network and Internet Connections category is not visible, click Switch to Category View in the upper left corner of the window.
3. Under the Dial-Up or LAN or High Speed Internet category, click the icon to select the connection that you want to help protect.
4. In the task pane on the left, under Network Tasks, click Change settings of this connection (or right-click the connection you want to help protect, and then click Properties).
5. On the Advanced tab, under Internet Connection Firewall, make sure the box is checked next to Protect my computer and network by limiting or preventing access to this computer from the Internet. If a check mark is in the box, the firewall is on. If the box is clear, the firewall is off and your computer is potentially vulnerable on the Internet.

If you have a different version of Windows, such as Windows 2000, Windows Millennium Edition, or Windows 98, you should obtain a hardware or software firewall from another company and install it.

You can check the manuals of your home networking devices, such as wireless access points or broadband routers, to determine if they include built-in hardware firewalls.

If you don't know if a software firewall is on your computer, you can check in the All Programs folder. Click Start, and then click All Programs. Look for a firewall program. Some common brand names for software firewalls for home users include McAfee, Symantec, and Tiny Personal Firewall.

If you don't know what operating system your computer is running, take the following steps:

• Click Start, and then click Run.
• In the Run dialog box, type winver. Click OK.

A dialog box appears that tells you which version of Windows software is installed on your computer.

If you're running Windows Vista or Windows XP SP2 or higher, Windows Firewall is already turned on. For more information, see Understanding Windows Firewall.

If you're running Windows XP without SP2 or SP3, you can download SP3 from Microsoft Update for free.

Windows Firewall monitors all network traffic on the connections for which it is enabled. The firewall keeps track of all communications that have originated from your computer, and it prevents unsolicited traffic from reaching your computer.

If necessary, the firewall dynamically opens ports and allows your computer to receive traffic that you have specifically requested, such as a Web page for which you have clicked the address.

A "port" is a networking term that identifies the point at which a type of network traffic reaches your computer. The exact ports that you open depend on the type of traffic you want to send and receive.

If you have not requested the incoming traffic, Windows Firewall helps block it before it can reach your computer. For special uses, such as networking, hosting online games, or hosting your own Web server, you can select ports that you want to leave open. This allows others to make connections to your computer, but it can also reduce security.

Windows Firewall is part of Windows Vista, Windows XP SP2 or higher Home Edition, and Windows XP SP2 or higher Professional.

To learn more read Using Windows Firewall and How to manually open ports in Internet Connection Firewall in Windows XP.

A firewall will not make your computer completely safe. However, a firewall provides the most effective first line of defense.

You should install a firewall first, and then add other security measures, such as updating your operating system, installing antivirus software and antispyware software, such as Windows Defender. Windows Defender comes with Windows Vista and it is available as a free download for Windows XP SP2 or higher.

You can use automatic updating to help make sure you are installing the available updates. See Protect your Computer for more information.

Yes. If you have more than one computer in a home or small-office network, you should protect every computer in the network.

Turning on Windows Firewall or another firewall on every connection will help prevent the spread of a virus from one computer to another in your network if one of your computers becomes infected. However, if you open an infected e-mail attachment, the firewall won't block it and it can infect your computer. You should install an antivirus program as well.

Yes. If you have multiple network connections on any of your computers, you should turn on the firewall for each connection. If you're running Windows Vista or Windows XP SP2, Windows Firewall is turned on automatically and it should not interfere with common tasks like file and print sharing.

For more information, see Firewall: Frequently Asked Questions for Windows Vista or Understanding Windows Firewall for Windows XP.

You should follow the policy established by the network administrator for your business, school, or organizational network.

In some cases, network administrators might configure all computers on the network so that you cannot turn on the firewall while your computer is connected to the network. The check box to turn on the firewall in the Windows Security Center or in the Network Connection Properties dialog box is unavailable. In those cases, you should ask your network administrator for guidance on whether you need a firewall on your computer.

Yes. Windows Vista and Windows XP users who want different features in a firewall may use a hardware firewall or a software firewall from another company.

No. Running multiple software firewalls is unnecessary for typical home computers, home networking, and small-business networking scenarios. Using two firewalls on the same connection could cause issues with connectivity to the Internet or other unexpected behavior.

One firewall, whether it is the Windows Firewall or a different software firewall, can provide substantial protection for your computer.

Yes. You should keep Windows Firewall turned on for all computers in your home network. This helps prevent the spread of viruses or worms across your network if a computer is infected. A computer on the network could become infected through a separate Internet connection, such as one on a laptop that is used on your home network and on public networks. Or a virus could be introduced to a computer on your network by way of e-mail or software installed from a CD.

Windows Firewall serves as the primary defense against a variety of computer worms that are transmitted over a network. A computer worm is similar to a virus, but is self-contained and can spread without the help of other programs. Windows Firewall helps to protect your computer by hiding it from external users and preventing unauthorized connections to your computer.

Windows Firewall in Windows Vista and Windows XP cannot protect against viruses that spread through e-mail, such as Trojan horses, which masquerade as helpful or benign software and trick you into opening or downloading them.

To help protect against viruses, use antivirus software. The firewall cannot prevent spam or pop-up ads.

To help protect against spyware and other unwanted software, try Windows Defender. Windows Defender comes with Windows Vista and it is available as a free download for Windows XP SP2.

The firewall will not prevent access to an otherwise unsecured wireless network. However, the firewall helps to protect the computers on your network, so if an intruder were to gain access to your network, he or she could not access your personal computer.

A firewall will help protect a computer on a wireless network, but will not restrict access to the network itself. You should configure your wireless network to use a network key using either Wi-Fi Protected Access (WPA) or wired equivalent privacy (WEP). For more information, consult the manual for your wireless networking devices.

To work correctly, some programs need to have specific ports open so that traffic can pass through the Windows Firewall.

For more information, see How to Open a Port in Windows Firewall.

This can be an issue if you enabled the firewall after sending the Remote Assistance invitation. To work around this problem, you can create a new Remote Assistance invitation while Windows Firewall is enabled, and then send the new invitation to the expert. For more information, see Allow Windows Remote Assistance to Communicate Through a Firewall.

To get more help with issues related to setting up a firewall on your computer or home network, see Firewall Frequently Asked Questions or What is a firewall?.