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1. PRESENTERS :-
VARUN SACHDEVA
ABHISHEK
KHYATI MATHUR
PRABHDEEP KAUR
Presentation :’Firewalls’
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2. Introduction
 FireWall is device that provides secure connectivity between
networks..
 A firewall may be a hardware, software, or a combination of
both that is used to prevent unauthorized programs or Internet
users from accessing a private network and/or a single computer.
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3. Hardware vs. Software Firewalls
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 Hardware Firewalls
 Protect an entire network
 Implemented on the router level
 Usually more expensive, harder to configure
 Software Firewalls
 Protect a single computer
 Usually less expensive, easier to configure

4. How does a software firewall work?
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 Inspects each individual “packet” of data as it arrives at either
side of the firewall
 Determines whether it should be allowed to pass through or if it
should be blocked

5. Types of Firewalls
 Common types of Firewalls:
1. Packet-filtering routers
2. Application-level gateways1
3. Circuit-level gateways1
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◦ Packet-filtering Router
• Applies a set of rules to each incoming IP packet
and then forwards or discards the packet
◦ Filter packets going in both directions
◦ The packet filter is typically set up as a list of
rules based on matches to fields in the IP or TCP
header
◦ Two default policies (discard or forward)

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Packet Filtering Firewall
Trusted
Network
Firewall
rule set
Packet is Blocked or Discarded
Untrusted
Network

8. 8
Packet Filtering Firewall
A packet filtering firewall is often called a network layer firewall
because the filtering is primarily done at the network layer (layer
three) or the transport layer (layer four) of the OSI reference
model.

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 Application-level Gateway
 Gateway sits between user on inside and server on outside. Instead of
talking directly, user and server talk through proxy.
 Allows more fine grained and sophisticated control than packet
filtering. For example, ftp server may not allow files greater than a set
size.
 A mail server is an example of an application gateway
◦ Can’t deposit mail in recipient’s mail server without passing through
sender’s mail server
host-to-gateway
ftp session
gateway-to-remote
host ftp session
application
gateway

10. 10
Application Gateways/Proxies

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Circuit-level Gateway
1. Stand-alone system
2. Specialized function performed by an Application-level Gateway
3. Sets up two TCP connections
4. The security function consists of determining which connections
will be allowed
5. Typically use is a situation in which the system administrator
trusts the internal users

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Circuit-level Gateway

13. Firewall Rules
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 Allow – traffic that flows automatically because it has been
deemed
 Block – traffic that is blocked because it has been deemed
dangerous to your computer
 Ask – asks the user whether or not the traffic is allowed to pass
through

14. Making The Firewall Fit
 IP address
 Domain names
 Protocols
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15. What It Protects You From
 Remote login
 Simple Mail Transfer Protocol session hijacking
 Operating system bugs
 Spam
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Conclusion

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What a personal firewall can do ?
• Stop hackers from accessing your computer.
• Protects your personal information.
• Blocks “pop up” ads and certain cookies.
• Determines which programs can access the Internet.
• Block invalid packets.

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• What a personal firewall cannot do ?
• Cannot prevent e-mail
viruses
– Only an antivirus product
with updated definitions can
prevent e-mail viruses.
• After setting it initially, you cannot forget about it
– The firewall will require periodic updates to the rulesets
and the software itself.

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Thank you