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Firewalls Presented By Bhavana Tapde


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  • 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
  • 4. Types of Firewall
    • Network Layer Firewall
    • Application Layer Firewall
    • Hybrid System
  • 5. 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.
  • 6. 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.
  • 7. 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.
  • 8. 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.
  • 9. 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.
  • 10. 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.
  • 11. Firewall Environments
    • DMZ Environment
    • VPN
    • Intranet
  • 12. 1. DMZ (Demilitarized Zone) Environment
    • DMZ network – neither a part of untrusted network nor trusted network, but connects both the networks.
  • 13. 2. VPN (Virtual Private Network)
    • Used to provide secure network links across networks.
    • Constructed on top of existing network media and protocol.
  • 14. 3. Intranet
    • Employs same types of services, applications, and protocols present in an Internet, without involving external connectivity.
    • Typically implemented behind the firewall.
  • 15. 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.
  • 16. 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.
  • 17. References
    • Matt Curtin, “Introduction to Network Security”,
    • Darren Bolding, “Network Security, Filters and Firewalls”,
    • 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
  • 18. Thank You!