Firewalls: Basic Principles and Some Implications

As part of the overall security plan, a firewall restricts access from one network to another network, with the goal of reducing or preventing the spread of unwanted or malicious programs or data. To do this, firewalls have developed capabilities roughly related to the three generations of firewalls: Packet Filtering, Circuit-Level (Stateful Packet Filtering), and Application Layer Firewalls. As firewalls enforce the information access policy, it is important for librarians to enter the discussion at early levels. In addition, an understanding of firewalls may help the librarian in diagnosing problems with patrons connecting to the information resources.