2. FIREWALL INSTALLATION A firewall is a protective system that prevents unauthorized access to your computer or network. A firewall also allows remote access to the network or computer through secure authentication certificates and admin logins. Firewall's can be either hardware or software. You should use both. Hackers scan the internet for computers and or networks that are not protected by a firewall so they can hijack or infect your computers with a virus, worm or a Trojan horse. Businesses and home users much use a firewall. Home computer users at a minimum should have a personal firewall, anti virus and anti spyware. Anti virus and anti spyware are not the same thing. Microsoft Windows XP with Service Pack 3 (SP3), Vista, Windows 7 & Windows 8 operating systems have a personal firewall system built in them. Never use two personal firewall products at the same time. Business Users should have much more.