Page 132 - DCAP309_INFORMATION_SECURITY_AND_PRIVACY

Information Security and Privacy Mithilesh Kumar Dubey, Lovely Professional University

Notes Unit 9: Firewalls

CONTENTS
Objectives
Introduction

9.1 Meaning
9.2 Demilitarized Zone (DMZ)
9.3 Proxy Servers

9.4 Packet Filtering
9.5 Screening Routers
9.6 Application Level Firewalls
9.7 Hardware Level Firewalls
9.8 Summary

9.9 Keywords
9.10 Review Questions
9.11 Further Readings

Objectives

After studying this unit, you will be able to:
 Understand the concept of Firewalls
 Discuss demilitarized zone, proxy servers, packet filtering, etc.
 Explain application level and hardware level firewalls

Introduction

A firewall is a dedicated appliance, or software running on another computer, which inspects
network traffic passing through it, and denies or permits passage based on a set of rules.
Firewalls 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, especially intranets. All messages entering or leaving the intranet
pass through the firewall, which examines each message and blocks those that do not meet the
specified security criteria.

In this unit, you will understand various concepts of firewalls.

9.1 Meaning

Basically, a firewall is a barrier to keep destructive forces away from your property. In fact,
that’s why its called a firewall.

A firewall is simply a program or hardware device that filters the information coming through
the Internet connection into your private network or computer system. If an incoming packet of

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