kousalya.s II-MSC CS 2017-2019 incharge staff: M.Florence Dyana

1. FIREWALL
PRESENTEDBY,
S.KOUSALYA,
II-M.sc., Computer Science.
BATCH:2017-2019
INCHARGE STAFF:
M.FLORENCE DYANA.

2. INTRODUCTION TO THE PAST
FIREWALL
 Idea came from construction industry in 19th century.
 Structure of metal sheets in houses, flights etc were the first
physical firewall.
 Metal sheets protected from fire.
 In 1980’s
 Usage of internet was rapidly growing.
 Businesses established and implemented networks.
 Difficulties faced !
 Huge network data traffic.
 Allocating the different networks.
 Solutions !
 Procedure of firewall implemented in routers.
 Networks were controlled.

3. PEOPLE WHO MADE IT IMPORTANT.
FIREWALL
 Clifford Stoll a US astronomer and computer expert, discovered that German spies accessing his
system. After this incident US started to implement firewall security in the government networks.
 Bill Cheswick the author of the famous security book “Firewalls and Internet Security” set up a
simple electronic jail to observe an attacker. He devoted himself and brought a huge impact on
awareness of firewall and internet and network security.
 Robert Tappan Morris created Morris Worm which was the virus that awakened all the network
administrator and made them think of the importance of firewall. The networks administrators
weren’t expecting anything like this. The worm spread around networks around the world.10% of
the internet was infected.

4. A FIREWALL:
FIREWALL
 A program or a hardware device.
 Filters packets.
 Unauthorized and authorized data goes through the filter.
 Unauthorized packets or data are blocked in and out of the network.
 Rules to the firewall are set and updated by the network administrator.
 Firewall sits between as a barrier between internet and internal network.

5. GENERATION OF FIREWALL
FIREWALL
The evolution of firewall and its categories
 Packet filters
 Circuit Level Gateways
 Proxy server/Application layer
 Stateful filters

6. PACKET FILTERS
FIREWALL
 Developed by Digital Equipment Corporation in 1988.
 Known to be the first filter system of its own kind.
 Bill Cheswick and Steve Bellovin researched and developed a working model
of packet filters.
 Packet filters inspects the packets.
 If the packets doesn't meet up with filtering rules.
 It is either rejected or dropped.
 Packet filters doesn't check whether the packet belongs to local
network.
 It filters the packets based only on information.

7. PACKET FILTERS
FIREWALL

8. CIRCUIT LEVEL GATEWAYS
FIREWALL
 It works at the session layer of the OSI reference model.
 Monitors TCP handshaking between packets.
 Determines whether a request session is valid.
 Used to hide information about the network.
 An example of circuit level gateways can be web browsing. As it only depends on the
packets between web browser and the internet

9. CIRCUIT LEVEL GATEWAYS
FIREWALL

10. PROXY SERVER/APPLICATION LAYER
FIREWALL
 Proxy server firewalls are also known as application layer firewall.
 AT&T Bell Laboratories developed the system.
 It requires separate network service configuration on the firewall.
 The rules for the services must be specified by network administrators.
 For example a firewall that supports HTTP, FTP and SMTP will not support Telnet, as
telnet rules are not specified in the firewall.

11. PROXY SERVER/APPLICATION LAYER
FIREWALL

12. STATEFUL FILTERS
FIREWALL
 It provides more protection than other filters.
 Uses methods from other filters.
 Multiple packet filtering.
 Denial-of-service attacks and other hacks can be reduced.