Firewall Definition
A firewall is a combination of software, hardware and policy which exists to control access to information on either side of the firewall. A firewall can exist between any two networks, but with the rise in popularity of the Internet, it is generally used to prevent Internet users from gaining access to a private or corporate network. In addition, it can be used to control which Internet services are available to users of the corporate network on the other side of the firewall . In general, a firewall provides a "choke point" between a trusted network and an untrusted network.A firewall is a pair of mechanisms, one which blocks traffic, and one which permits traffic. ... The important factor is that a firewall merely provides a means to implement an access control policy which should be decided on in advance - it does not provide the policy along with the software. A firewall is often installed on a machine which is separated from the rest of the trusted network. ... Instead, some specific kinds of firewalls will be described in detail The Benefits of a Firewall · Protection from Vulnerable Services Firewalls can be configured to filter out inherently dangerous services, exposing the protected network to fewer risks. For example, a firewall could block services such as NFS from entering or leaving the protected subnet. ... · Logging and Statistics As all Internet access passes through a firewall, the firewall can log accesses and calculate statistics about network usage. ... A firewall may even be able to provide a tracing facility, in order to determine where the attack or probe originated (or claims to have originated). · Policy Enforcement A firewall provides a means of implementing a security policy.