Employing Proxy Services

INTRODUCTION As the use of the TCP/IP protocol suite expanded during the 1990s in tandem with the growth in the use of the Internet, organizations began to realize a new security threat emerging as their networks were connected to the Internet. As academic, government, and commercial networks were connected to the Internet, they became subject to attack from literally an unlimited number of computer users located throughout the world. Although router access-lists provide a mechanism to enable or disable the flow of packets through router ports, based on source and destination IP address and the type of application data expressed in the form of a port number, organizations began to realize that by themselves router access-lists were not a sufficient barrier to prevent many types of undesirable operations against hosts residing behind a router. One solution developed to provide a higher level of security to organizational networks was the use of a firewall with proxy service capability located behind the router — which is the focus of this article. This article will first review the operation of router access-lists and some of their limitations. Using this information as a base, a description and discussion of the operation of different types of firewall proxy services and how they can be used to obtain an enhanced level of network protection will follow.