13.-+Firewall

A **firewall** is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass. A firewall is a set of related programs, located at a network [|gateway] [|server], that protects the resources of a private network from users from other networks. (The term also implies the security policy that is used with the programs.) 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 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. Computer security borrows this term from firefighting, where it originated. In firefighting, a firewall is a barrier established to prevent the spread of fire. LOOK TO THIS VIDEO []