A firewall program or hardware device filters the information coming through the Internet connection into a network. Without a firewall in place, all the computers on a network are directly accessible to anyone on the Internet. One mistake can open a security hole and hackers can get to the machine and exploit the hole.

With a firewall a businsess can:

Place a firewall at every connection to the Internet and sets up security rules permiting only one of them to receive public FTP traffic.

Set security rules for FTP servers, Web servers, and Telnet servers.

Control how employees connect to Web sites, whether files are allowed to leave the company over the network, allowing tremendous control over how people use the network.

Firewalls are customizable allowing filters to be added or removed based on several conditions. Some of these are: IP addresses, domain names, protocols, ports, and specific words and phrases.