The Internet is a world-wide collection of networks that all use a common protocol for communications. Many organizations are in the process of connecting to the Internet to take advantage of Internet services and resources. Businesses and agencies are now using the Internet or considering Internet access for a variety of purposes, including exchanging e-mail, distributing agency information to the public, and conducting research. Many organizations are connecting their existing internal local area networks to the Internet so that local area network workstations can have direct access to Internet services.
Internet connectivity can offer enormous advantages, however security needs to be a major consideration when planning an Internet connection. There are significant security risks associated with the Internet that often are not obvious to new (and existing) users. In particular, intruder activity as well as vulnerabilities that could assist intruder activity are widespread. Intruder activity is difficult to predict and at times can be difficult to discover and correct. Many organizations already have lost productive time and money in dealing with intruder activity; some organizations have had their reputations suffer as a result of intruder activity at their sites being publicized.
This publication focuses on security considerations for organizations considering Internet connections as well as for organizations already connected to the Internet. In particular, this document focuses on Internet firewalls as one of the mechanisms and methods used for protecting sites against Internet-borne threats. This document recommends that organizations use firewall technology and other related tools to filter connections and limit access. This document is an expansion of the issues and guidance contained in NIST CSL Bulletin, Connecting to the Internet: Security Considerations [NIST93].