Learn how a firewall works in this Crash Course -- then follow our Learning Guide links for more information on types of firewalls, how to select a firewall and position it within your network, and how to manage and maintain a firewall.
Firewalls protect the network, and are a must-have in every network administrator's environment. But what exactly do they do? In the past few years, the role of the firewall has blurred -- it is no longer always a physical box or tangible piece of hardware, and the perimeter of the network is often difficult to discern. Sometimes the firewall is integrated into a switch or a VPN appliance, and sometimes it's a downloadable software program. So how can you keep tabs on your firewall? The first step is to understand exactly what it does.
A firewall is a set of related programs that protects the resources of a private network from users from other networks. An enterprise with an intranet that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to.
Basically, a firewall, working closely with a router program, examines each network packet to determine...
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whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.
There are a number of firewall screening methods. A simple one is to screen requests to make sure they come from acceptable (previously identified) domain name and Internet Protocol addresses. For mobile users, firewalls allow remote access in to the private network by the use of secure logon procedures and authentication certificates.
A number of companies make firewall products. Features include logging and reporting, automatic alarms at given thresholds of attack, and a graphical user interface for controlling the firewall. (Information courtesy of Whatis.com.)
Browse our Network Security Best Practices and Products section to learn more about firewalls and other network security technologies.
