The increasing complexity of networks, and the need to make them more open due to the growing emphasis on and attractiveness of the Internet as a medium for business transactions, mean that networks are becoming more and more exposed to attacks, both from without and from within. The search is on for mechanisms and techniques for the protection of internal networks from such attacks. One of the protective mechanisms under serious consideration is the firewall. A firewall protects a network by guarding the points of entry to it. Firewalls are becoming more sophisticated by the day, and new features are constantly being added, so that, in spite of the criticisms made of them and developmental trends threatening them, they are still a powerful protective mechanism. This article provides an overview of firewall technologies.

Originally Published in, to Wit Telektronikk Vol. 96 No.3-2000, ISSN 0085-7130, 47-52, 2000