You might have a firewall already and not know it – your DSL or Cable modem may have a firewall built-in. Look on the label to see what kind of device you have. Log in to your Internet provider’s web site and check whether your modem has a built-in firewall. If it doesn’t, ask to be upgraded.
If you have a laptop computer and access the Internet via WiFi “hotspots” in cafes, libraries, or other locations, you need a firewall even if your home router has a firewall built-in.
You can also install a personal firewall program on each PC in your house. If you have Windows XP or Vista, a firewall is provided with Windows but you need to activate it.
Instructions: Activate Windows XP firewall. Activate Windows Vista firewall.
Or, you can install Zone Alarm or Comodo firewall. Both are easy to install and use.
Zone Alarm: www.zonelabs.com
Test your firewall to see if it is working: Site 1: (www.auditmypc.com), Site 2: (www.grc.com/) (You can consider these to be trusted web sites).