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  • 1. FIREWALLS Antonio Arthur
  • 2. Question
    • What is a firewall?
    • Describe with examples the different types of firewalls.
    • Describe the drawbacks of each type of firewall and known successful attacks
  • 3. What is a firewall?
    • A firewall is defined as a security system that prevents outside users from accessing private network resources. They can be set up between segments of a network, but are usually used to improve security between the internet and a network.
    • In order to understand the concept, it is useful to think of a castle with a mote dug around it. All traffic into and out of the castle, is thus forced to pass over the single drawbridge. The drawbridge is like the firewall (See diagram 1).
  • 4. Diagram 1
  • 5. Different types of firewalls
    • There are 2 main types of firewalls:
      • 1. Packet-level Firewalls
      • 2. Application-level Firewalls
  • 6. Packet-Level Firewall
    • Packets are allowed or denied access based on source and destination IP addresses.
    • Router which has been configured with IP address filtering rules is used to screen out data from unidentified sources.
    • Weakness : susceptible to IP spoofing.
    see example below
  • 7. VisNetic Firewall 2.2, Software
  • 8. Application-Level Firewall
    • Uses additional software, called a proxy, to filter incoming or outgoing data. Most secure firewall.
    • Data is screened on the basis of content as opposed to IP addresses.
    • Drawbacks: causes noticeable speed decrease, may be susceptible to attacks from inside the network. (e.g. sasser worm, see slide 11)
    see example below
  • 9. SonicWall Pro 2040, Hardware Price: $2,000 Data Transfer Rate: 200 Mbps Port Qty: 5
  • 10. Common Network Layout
  • 11. Successful Attacks
    • Sasser worm
      • Although there may be an actual firewall between the internal network, and the Internet, the virus can be spread once a computer (this may be for example, a laptop brought onto the network) on the internal network becomes infected. It then propagates itself, without user help. Results in the shutdown message shown below.
  • 12.  
  • 13. Successful Attacks
    • IP Spoofing
    • IP spoofing is a fairly simple concept. It simply involves changing the source address in the IP header file.
    • see diagram below
  • 14.  
  • 15. Why firewalls are so important
    • There is a tendency among local businesses to overlook the importance of security. These business generally adopt the attitude that it ‘couldn’t happen to them’. On Wednesday, September 22 nd , 2004, the nation newspaper company, and the Starcom Network Company were both proven wrong in this belief as both their websites were hacked.(nationnews.com, vob929.com)
    • The screenshot below shows the contents of the nation website on the day in question.
  • 16.