A brief introduction and working of a firewall.

1. BY K.VIDYA MADHURI
IT-F1
ROLL NO- 14311A1201
FIREWALLS

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

3. WHAT IS A FIREWALL?

4. • 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

5. • 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.

6. • 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.

7. TYPES OF FIREWALLS
An illustration of
where a firewall can
be located in a
network.

8. • 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.

9. • 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.

10. HOW A FIREWALL WORKS?

11. • 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.

12. 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

13. 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.

14. • 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

15. THANK YOU!!