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The Firewall Essay

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The Firewall

WHAT IS A NETWORK FIREWALL?
A firewall is a system or group of systems that enforces an access control policy between two or more networks. The means by which this control is accomplished varies widely, but in principle, the firewall is a pair of mechanisms, one that blocks traffic and one that permits traffic. Some firewalls emphasize blocking traffic, while others emphasize permitting traffic. The most important thing to recognize about a firewall is that it implements an access control policy. If you don't know what kind of access you want to permit or deny, or you let someone else or some product configure a firewall based on judgment other than yours, that entity is making policy for your whole organization.

WHY …show more content…

Generally, firewalls are configured to protect against unauthenticated interactive logins from the outside world. This protection, more than anything, helps prevent vandals from logging on to machines on your network. More elaborate firewalls block traffic from the outside to the inside but permit users on the inside to communicate freely with the outside. The firewall can protect you against any type of network-borne attack if you unplug it.

Firewalls are also important because they are a single point where you can impose security and auditing. If someone attacks a computer system by dialing in with a modem, tracing the perpetrator is impossible. In contrast, the firewall can act as an effective phone tap and tracing tool. Firewalls also provide an important logging and auditing function, summarizing topics such as the kinds and amount of traffic that passed through it and how many attempted break-ins occurred recently.

WHAT CAN'T A FIREWALL PROTECT AGAINST?
Firewalls can't protect against attacks that don't go through the firewall. Many corporations that connect to the Internet are very concerned about proprietary data leaking out of the company. Unfortunately, a magnetic tape exports data just as effectively as the Internet. Many organizations whose management is terrified of Internet connections have no coherent policy about protecting dial-in access via modems. It's silly to build a steel door six feet thick

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