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Chapter5 Firewall

Chapter5 Firewall. Ku-Chuan Lin. Outlines. Defining an access control policy Understanding firewalls Firewall functions Firewall Types Choosing a firewall type Additional firewall considerations Q & A. Defining an Access Control Policy. Direction Service Specific Individual Users

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Chapter5 Firewall

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  1. Chapter5Firewall Ku-Chuan Lin Chapter5 Firewall

  2. Outlines • Defining an access control policy • Understanding firewalls • Firewall functions • Firewall Types • Choosing a firewall type • Additional firewall considerations • Q & A Chapter5 Firewall

  3. Defining an Access Control Policy • Direction • Service • Specific • Individual Users • Time of Day • Public or Private • Quality of Service • Role Chapter5 Firewall

  4. Definition of a Firewall • A firewall is a system or group systems that enforce an access control policy on network traffic as it pass through access points. Chapter5 Firewall

  5. When is a Firewall Required？ • Dial-In Modem Pool and Client-Initiated VPN • External Connections to Business Partners • Between Departments • Hosts Chapter5 Firewall

  6. Firewall Functions • Static Packet Filtering • Dynamic Packet Filtering • Stateful Filtering • Proxy Servers Chapter5 Firewall

  7. Static Packet Filtering • Protocol • Destination IP address or subnet • Source IP address or subnet • Destination service port • Source service port • Flag ( TCP only ) Chapter5 Firewall

  8. Valid TCP Flag • ACK ( Acknowledgment ) • FIN ( Final ) • PSH ( Push ) • RST ( Reset ) • SYN ( Synchronize ) • URG ( Urgent ) Chapter5 Firewall

  9. Dynamic Packet Filtering • Dynamic Packet Filtering in Action • UDP Traffic and Dynamic Packet Filtering • Is my transport supported？ Chapter5 Firewall

  10. Dynamic Packet Filtering in Action Dynamic Packet Filter State Table Protected Host has a open session with Remote Server Source Port=1037 Destination Port=80 Attacker Remote Server Protected Host ACK=1 FIN=1 ACK = 1 PSH=1 ACK = 1 FIN = 1 FIN = 1 Chapter5 Firewall

  11. UDP Traffic and Dynamic Packet Filtering • Static packet filtering has some real problems handling UDP traffic. • Dynamic Packet Filtering does not rely on information within the packet header. Chapter5 Firewall

  12. Is my transport supported？ • The implement of dynamic packet filtering is transport specific. • It has to be specifically implemented for each protocol transport, such as TCP, UDP and ICMP. Chapter5 Firewall

  13. Stateful Filtering • The greatest addition that stateful filtering provides to dynamic filtering is the ability to maintain application state, not just connection state. • First implemented by Check Point under the name Stateful Multilevel Inspection. Chapter5 Firewall

  14. Proxy Servers • A proxy server is an application that mediates traffic between two network segments. • With the proxy acting as mediator, the source and destination systems never actually “connect”. Chapter5 Firewall

  15. How A Proxy Passes Traffic？ HTTP Application Data Request Data Request Proxy Server Internal Host Remote Server Chapter5 Firewall

  16. Filtering Hostile Code • Proxies can analyze the payload of a packet of data and make decision as to whether this packet should be passed or dropped. Chapter5 Firewall

  17. Firewall Types • Embedded Firewalls • Known as choke-point firewalls • Software Firewalls • Hardware Firewalls • Application Firewalls Chapter5 Firewall

  18. Which Type Should I Choose？ • Server-Based Firewalls • Appliance-Based Firewalls • Cisco PIX • Check Point Firewall-1 Chapter5 Firewall

  19. Additional Firewall Considerations • Address Translation • Firewall Logging and Analysis • Virtual Private Networks ( VPNs) • Intrusion Detection and Response • Integration and Access Control • Third-Party Tools • You Decide Chapter5 Firewall

  20. Summary • Keep in mind the basic types and services that all firewalls offer, including： • Static/Dynamic/Stateful/Proxy filtering • VPN capabilities • Monitoring, logging and analysis • Extra services and third party product integration Chapter5 Firewall

  21. Q & A Chapter5 Firewall

  22. Question 1Firewall Deployment Internet Router A DMZ B Internal Network Web Server E-mail Server File Server Email Server Workstation Workstation Chapter5 Firewall

  23. Question 2 What is FIN Scanner? Chapter5 Firewall

  24. Question 3 Please compare server-based Firewalls with appliance-Based Firewalls？ Chapter5 Firewall

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