This is a background operation, all but invisible to the customer. But the technology allows web site owners to control access to particular servers if they so wish, and to files or to services which contain sensitive information. They allow that information to be shared with the browser if appropriate, while hiding it from any third party. Firewalls Firewalls are what the name implies walls that hamper or totally halt penetration by those who have no authority to pass through them Every Internet connection should have a firewall as another line of defence against abuse. There are three types, packet filters, Stateful Inspection firewalls, and Applications Gateways, and each has a particular strength.
Some companies implement more than one system at a time.
Packet filters screen information coming in to allow access or refuse it based on a set of predetermined rules. They examine the data and what it wants to do and then check that the request is permissible within the corporation. If not, then entry is refused. Stateful Inspection firewalls extend inspection of the data and have a wider band of permission they will admit the data if it comes inside set parameters. An Application Gateways acts as an intermediary between two systems.