In effect, network security must provide an electronic counterpart to the perimeter security that protects the physical computer installation. A common tool used to meet the requirements of good network security is a firewall computer . The firewall computer acts as a gatekeeper, managing every request for data from the outside world and allowing or denying data requests into the network based on a sophisticated set of rules. The firewall controls and logs every attempt to access the data on the protected system. Although firewall is a new word for many computer users, the concept is not.
Firewalls act much like the manager of a safe deposit box vault.
For example, when you visit the bank to get some items from your safe deposit box, you aren't allowed to walk into the vault, pull out any box you want, remove papers from the box, and then leave without speaking to anyone. Instead, you must first check in with the safe deposit manager at the front desk. The manager checks your identification, confirms who you are with a signature card, and then escorts you to your safe deposit box. Together, you access your safe deposit box using two separate keys. Then the manager escorts you to a private area where you can transact your business out of sight of other bank customers.