Firewalls

1
Firewalls

• Presented By
• Bhavana Tapde
• March 21, 2006

2
Outline

• Introduction
• Types of Firewall
• Firewall Environments
• Limitations of Firewall
• Conclusion

3
Introduction

• A Firewall
• group of components that monitors all traffic to
  and from a site and maintains a barrier between
  two networks.
• network gateway that enforces security rules on
  peer-to-peer communication.
• provides a single choke-point that keeps
  unauthorized users out of the protected network.
• The purpose of firewall
• Perimeter Security
• Server Protection
• IP Filtering inside the network

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Types of Firewall

• Network Layer Firewall
• Application Layer Firewall
• Hybrid System

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1. Network Layer Firewall

• Packet filtering is done.
• Packet Filtering examine incoming and outgoing
  packets allow or disallow their transmission or
  acceptance on basis of set of configurable rules,
  called policies.
• Policies may be based upon IP address, port, or
  protocol.

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1. Network Layer Firewall (cont)

• Screened Host Firewall
• Access to and from a single host is controlled by
  means of a router operating at network layer.
• Bastion Host Computer that acts like gateway
  between inside and outside networks, and controls
  access between both the networks.

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1. Network Layer Firewall (cont)

• Screened Subnet Firewall
• Access to and from a whole network is controlled
  by means of a router operating at network layer.

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2. Application Layer Firewall

• Also known as Proxy Gateways.
• These are made up of bastion hosts that run
  special software to act as a proxy server.
• Client program establishes connection with
  application gateway or proxy, that in turn
  establishes connection with the destination
  service.
• Communication is between client and destination
  service is via proxy, to hide and protect the
  inside network.

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2. Application Layer Firewall (cont)

• Dual Homed Gateway
• Highly secured host that runs proxy software.
• Has two network interfaces, one for each network
  and blocks traffic passing through it.

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3. Hybrid System

• Uses principles of both, application gateway and
  packet filtering.
• New connection is authenticated and approved at
  application layer and remainder of connection is
  passed to session layer, where packet filtering
  is done.

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Firewall Environments

• DMZ Environment
• VPN
• Intranet

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1. DMZ (Demilitarized Zone) Environment

• DMZ network neither a part of untrusted network
  nor trusted network, but connects both the
  networks.

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2. VPN (Virtual Private Network)

• Used to provide secure network links across
  networks.
• Constructed on top of existing network media and
  protocol.

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3. Intranet

• Employs same types of services, applications, and
  protocols present in an Internet, without
  involving external connectivity.
• Typically implemented behind the firewall.

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Limitations of Firewall

• Firewall cannot protect against
• attacks that do not pass through the firewall,
  because firewall is not the only entry point of
  network.
• internal threats.
• the transfer of virus protected files, since
  viruses are normally hidden in expected traffic
  like email messages or HTML code.

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Conclusion

• It is clear that some form of security is
  essential for private networks connected to
  Internet or other networks.
• A firewall is an important and necessary part of
  that security, but cannot be expected to perform
  all the required security functions.

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References

• Matt Curtin, Introduction to Network Security,
  http//www.interhack.net/pubs/netywork-security/
• Darren Bolding, Network Security, Filters and
  Firewalls, http//www.acm.org/crossroads/xrds-1/s
  ecurity.html
• G.D.Leat and Gert S., Network Security
  Fundamentals. Indianapolis Cisco Press, 2005,
  pp. 159-190
• A.S.Tanenbaum, Computer Networks. India Pearson
  Education, 2004, pp. 776-780

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Thank You!