FIREWALLS Antonio Arthur

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FIREWALLS Antonio Arthur
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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

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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).

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Diagram 1
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Different types of firewalls

• There are 2 main types of firewalls
• 1. Packet-level Firewalls
• 2. Application-level Firewalls

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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
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VisNetic Firewall 2.2, Software
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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
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SonicWall Pro 2040, Hardware
Price 2,000 Data Transfer Rate 200 Mbps Port
Qty 5
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Common Network Layout
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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.

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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

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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
  couldnt happen to them. On Wednesday,
  September 22nd, 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.

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