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1. Firewall
Design
&
Implementation Issues
Prepared by : Kunal Kumar
Submitted to : Ms. Hanisha Chhabra

2. Contents
 Origin of Firewall
 Introduction
 What a Firewall actually means ?
 Needs
 History
 Types
 Design and Implementation Issues
 Policies
 Conclusions

3. Origin of concept of Firewall
 With the rapid growth of the internet and security
flaws in operating system, network security has
become a major concern for the organizations
throughout the world.
 Also the hacking tools needed to penetrate the
security of corporate networks are widely used.
 Because of this increased focus on network
security, network administrators worked over this
issue and developed a tool called as Firewall.

4. Introduction
Blocks Unauthorized access: A Firewall is a part of computer system
and computer network which is designed to BLOCK the
unauthorized access while permitting authorized connection.
 Physical Firedoors: Its job is similar to a physical firedoors that keeps
a fire from spreading from one area to another.
 Hardware and/or Software: It can be implemented either as a
software or a hardware or the combination of both.
 Firewall protects the network from unauthorized use by attackers.

5. What a Firewall actually means ?
 A firewall is a BARRIER to keep destructive
forces away from our property/ assets. In fact,
that is why it is called a Firewall.
 In other words, it is a device or set of devices
which is configured to permit or deny computer
applications based upon set of rules and criteria.

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Second level
● Third level
● Fourth level
● Fifth level

7. Why Firewalls are needed ?
 Remote log-in :- This is when someone
is able to connect to a computer and
control it in some form.
 VIRUS :- The most common threat is
computer virus. A virus is a small program
that can copy itself to other computer.

8. Why Firewalls are needed ?
 SOURCE ROUTING :- In most of the cases,
the path taken by a packet to travel over the
internet is determined by the routers along that
path. But sometimes source itself specify the
route through which the packet have to travel.
Hackers sometimes take advantage of this
source routing. Firewall simply DISABLE
source routing by Default.

9. Firewalls History
 First generation - Packet filters
This firewall technology was in 1988 by Jeff Mogul from Digital
Equipment Corporation (DEC).
 Second generation - Circuit level
From 1980-1990 two colleagues from AT&T Company,
developed the second generation of firewalls known as circuit level
firewalls.
 Third generation - Application layer
Gene Spafford of Purdue University, Bill Cheswick at AT&T
Laboratories described a third generation firewall. also known as
proxy based firewalls.

10. Types of Firewall
 Packet filtering
 Circuit level gateway
 Application level firewall

11. Packet Filtering
 First generation of Firewall.
 Also known as Screening routers and
Filtering routers.
 Operates at Network layer or Transport layer
of OSI Model.
 Routers are used to protect Intranet by blocking
certain packets that’s why they are called Filtering
or Screening routers.

12. Packet Filters

13. Circuit level gateway
 2nd generation of Firewall.
 Operates at Session layer of the OSI model, or TCP/IP
layer of the TCP/IP.
 They monitor TCP handshaking between packets to
determine whether a requested session is legal. Traffic is
filtered based on the specified session rules, such as when
a session is initiated by the recognized computer.

14. Circuit level gateway

15. Application level Firewall
 3rd Generation firewall.
 Also known as Proxy Firewalls.
 Operates at Application layer of OSI or
TCP/IP model and hence known as
Application layer Firewall.
 It works like a proxy—middleman, agent,
substitute which has the authority to represent
someone else

16. Firewalls - Application Level
Gateway (or Proxy)

17. Design and Implementation
Issues
 The first and most important decision reflects the policy of
how our organization wants to operate the system.
 All traffic from inside to outside and vice-versa must pass to
the firewall which can be achieved by physically locking all
access to the local network accepted to the firewall.
 Only authorized packet defined by local security policy will be
allowed to pass.
 Financial Issues : Complete firewall may be higher in cost.

18. Conclusions
 Don’t make the mistake of thinking that no one will attack your
network, because with the rise in automated attack tools,
your network is as much at risk as every other network on the
Internet.
 Nearly every organization connected to the Internet has installed
some sort of firewall.
 When choosing and implementing a firewall solution, make a
decision based on the organization's needs, security
policy, technical analysis, and financial resources.
Solutions available today utilize different types of equipment,
network configurations, and software.

20. ...Thankew...
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