12. Firewalls

The rapid growth of the Internet has led to a corresponding growth of both users and activities in cyberspace. Unfortunately, not all these users and their activities are reputable; thus, the Internet has been increasingly, at least to many individuals and businesses, turning into a “bad Internet.” Bad people are plowing the cyberspace with evil activities that include, among other things, intrusion into company and individual systems looking for company data and individual information that erodes privacy and security. There has, therefore, been a need to protect company systems, and now individual systems, keeping them out of access from those “bad users” out on the “bad Internet.” As companies build private networks and clouds connect the Internet, network security becomes one of the most important concerns network system administrators face. In fact, these network administrators are facing threats from two fronts: the external Internet and the internal users within the company network. Thus, system administrators must be able to find ways to restrict access to the company network or sections of the network from both the “bad Internet” outside and from unscrupulous inside users. Such security mechanisms are based on a firewall. A firewall is a hardware, software, or a combination of both that monitors and filters traffic packets that attempt to either enter or leave the protected private network. It is a tool that separates a protected network or part of a network, and now increasingly a user device from an unprotected network—the “bad network” such as the Internet. In many cases, the “bad network” may even be part of the company network. By definition, a “firewall” is a tool that provides a filter of both incoming and outgoing packets. The chapter focus on the firewall and its role in network security.