Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Keeping Your Site Comfortably Secure: An Introduction to Internet Firewalls



John P. Wack, Lisa J. Carnahan


This document provides an overview of the Internet and security-related problems. It then provides an overview of firewall components and the general reasoning behind firewall usage. Several types of network access policies are described, as well as technical implementations of those policies. Lastly, the document contains pointers and references for more detailed information. The document is designed to assist users in understanding the nature of Internet-related security problems and what types of firewalls will solve or alleviate specific problems. Users can then use this document to assist in purchasing or planning a firewall.
Special Publication (NIST SP) - 800-10
Report Number


computer security, firewalls, Internet


Wack, J. and Carnahan, L. (1994), Keeping Your Site Comfortably Secure: An Introduction to Internet Firewalls, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD (Accessed May 28, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created December 1, 1994, Updated May 4, 2021