BY K.VIDYA MADHURI IT-F1

ROLL NO- 14311A1201

FIREWALLS

• FIREWALL-INTRODUCTION• BRIEF HISTORY OF FIREWALLS• TYPES OF FIREWALLS• HOW A FIREWALL WORKS• APPLICATIONS

CONTENTS

WHAT IS A FIREWALL?

• A firewall is a system designed to prevent unauthorized access to or from a private network.• 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

FIREWALL-INTRODUCTION

• Firewall technology emerged in the late 1980s when the Internet was a fairly new technology in terms of its global use and connectivity. • The predecessors to firewalls for network security were the

routers used in the late 1980s.

BRIEF HISTORY OF FIREWALLS

The early firewall settings showing the incoming and outgoing traffic.

• Clifford Stoll's discovery of German spies tampering with his system.• Bill Cheswick's "Evening with Berferd" 1992, in which he set up a

simple electronic "jail" to observe an attacker.

TYPES OF FIREWALLS

An illustration of where a firewall can be located in a network.

• Network layer firewalls: Network layer firewalls, also called packet filters, operate at a relatively low level of the TCP/IP protocol stack, not allowing packets to pass through the firewall unless they match the established rule set. The firewall administrator may define the rules; or default rules may apply.• Application layer firewalls: Application-layer firewalls work on the

application level of the TCP/IP stack (i.e., all browser traffic, or all telnet or ftp traffic), and may intercept all packets traveling to or from an application. They block other packets (usually dropping them without acknowledgment to the sender).• Proxies: A proxy server (running either on dedicated hardware or as

software on a general-purpose machine) may act as a firewall by responding to input packets (connection requests, for example) in the manner of an application, while blocking other packets. A proxy server is a gateway from one network to another for a specific network application, in the sense that it functions as a proxy on behalf of the network user.

• There are also other types of firewalls: Hardware firewalls and software firewalls.• Hardware firewalls employ hardware devices like broadband

routers for protecting networks.• Software firewalls employ a software running on the host computer

to ensure the network protection.

HOW A FIREWALL WORKS?

• There are two access denial methodologies used by firewalls. A firewall may allow all traffic through unless it meets certain criteria, or it may deny all traffic unless it meets certain criteria.• Firewalls may be concerned with the type of traffic, or with source

or destination addresses and ports. They may also use complex rule bases that analyze the application data to determine if the traffic should be allowed through.• The type of criteria used to determine whether traffic should be

allowed through varies from one type of firewall to another like IP addresses, protocols, ports and domains.

At a personal level, firewall does the following things:•Block or alert the user about all unauthorized inbound or outbound connection attempts.•Allows the user to control which programs can and cannot access the local network and/or Internet and provide the user with information about an application that makes a connection attempt.•Hide the computer from port scans by not responding to unsolicited network traffic.•Monitor applications that are listening for incoming connections.•Monitor and regulate all incoming and outgoing Internet users.•Prevent unwanted network traffic from locally installed applications.•Provide information about the destination server with which an application is attempting to communicate.

APPLICATIONS OF FIREWALLS

Anyone who is responsible for a private network that is connected to a public network needs firewall protection. Furthermore, anyone who connects so much as a single computer to the Internet via modem should have personal firewall software.

• Firewalls cannot enforce your password policy or prevent misuse of passwords. • Firewalls cannot protect you from poor decisions.• Firewalls cannot protect you when your security policy is too lax.• Firewalls cannot stop internal users from accessing websites

with malicious code, making user education critical.

LIMITATIONS OF FIREWALLS

THANK YOU!!