What is a network firewall? What types of firewalls are there, and which kind best protects enterprise data? All of these questions, and more, are answered in our network security firewall guide. This tutorial will help you learn every kind of firewall -- from unified threat management (UTM) to proxys -- and give you advice on firewall purchasing, firewall placement and firewall maintenance and management.

For those new to the technology, skip below the table of contents to see firewalls defined and category types. If you're well-acquainted with this essential part of security, then you are encouraged to navigate the table of contents below to drill down into topics you'd like to learn more about, whether it be on firewall implementation or on how to choose an enterprise firewall for your company's needs.

Introduction to firewalls
Types of firewalls
      → Network layer
      → Application layer
      → Proxy
      → UTM
Choosing a firewall
      → Who is responsible for firewalls?
      →  Security risk assessment
      → Firewall purchasing advice
Firewall implementation and placement
      → Placement of a firewall
      →  Are two firewalls better than one?
      →  Firewall implementation precautions
Firewall management and maintenance

INTRODUCTION TO FIREWALLS

A firewall is a hardware or software system that prevents unauthorized access to or from a network. They can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet. All data entering or leaving the Intranet pass through the firewall, which examines each packet and blocks those that do not meet the specified security criteria.