Proxy Firewalls

John D. McLaren, Murray State University

Introduction

Proxy Terminology

Houston, We Have a Proxy

Definition of Firewall

The Application Layer Gateway

The Application Layer Firewall

The NAT-ing Firewall

Why and When to Use a Proxy

Goals of a Proxy Firewall

Advantages of Proxy Firewalls

Disadvantages of Proxy Firewalls

Proxy Characteristics and Capabilities

Building a Proxy

Proxy Firewall Characteristics

Summary of Capabilities

Proxy Protocols

Types of Proxies

Store-and-Forward Servers

Application versus Circuit-Level Proxies

Forward versus Reverse Proxies

Application Firewalls

Caching Proxies/Web-Caching Proxies

Proxy Configurations

System Configuration

Network Configuration

Case Study: Traffic Analysis of a Proxy Operation

Details on the Proxy Scenario

Conclusion

Glossary

Cross References

Further Reading

INTRODUCTION

As network security issues continue to dominate the world of networking, new devices and software are constantly surfacing. Proxy firewalls are just one of the players that are receiving more attention lately. Proxies have been around for a long while, but their primary purpose historically has been to serve as Web accelerators.

The endless variety of the application layer contents make it ripe for potential security vulnerabilities; there is a need for more detailed traffic analysis. Things such as viruses and spam cannot be discovered using simple packet-filtering firewalls. The solution to issues such as these is application layer and proxy firewalls. ...

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