A firewall can block malware that could otherwise scan your computer for vulnerabilities and then try to break in at a weak point. The only way to make a home computer 100 secure is to turn it off or disconnect it from the Internet. The real issue is how to make one 99.9 secure when it is connected. At a minimum, home computers need to have personal firewall and antimalware software installed and kept uptodate to find and remove viruses, spyware, Trojans and other malware. A home network that uses a wired or wireless router with firewall features provides additional protection.

Website: http://www.firewallguide.com/