A firewall is a security device which can be either hardware and/or software based. The purpose of a firewall is to permit or deny proxy data coming in and out of your computer system and/or network. Firewalls are configured according to the requirements set by the individual. From a single computer Firewall which is installed software that denies phishing and ID theft attacks from the internet. With advanced Firewalls on a network, which consists of a hardware device and software that is custom configured by a network administrator to keep the network secure.