Zone Alarm

If you have cable modem or DSL service, your ISP probably have a firewall, and it may do a good job of preventing intrusion into your system. A home firewall is still a good idea, though. A firewall is software that keep viruses and intruders out of your PC, usually by blocking the data ports that are your PC's entry points. MCAfee and Norton offer firewall programs, but there is also Zone Labs' Zone Alarm,which is freeware.