Introduction to Firewalls

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Introduction to Firewalls

• TEC 236

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What is a Firewall?

• A firewall is hardware, software, or a
  combination of both that is used to prevent
  unauthorized programs or Internet users from
  accessing a private network and/or a single
  computer

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What is a Firewall?

• A security system that acts as a protective
  boundary between a
• network and the outside world
• Isolates a computer or network from the outside
  based on a defined set of rules
• Inspects each individual "packet" of data as it
  arrives at either side of the firewall
• Maintains a state table
• Determine whether traffic should be allowed to
  pass or be blocked

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Rules Determine
WHO ? WHEN ? WHAT ? HOW ?
INTERNET
My PC
Protected Network
Firewall
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Hardware vs. Software Firewalls

• Hardware Firewalls
• Protect an entire network
• Implemented on the router level
• Usually more expensive, harder to configure
• Software Firewalls
• Protect a single computer
• Usually less expensive, easier to configure

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How does a software firewall work?

• Inspects each individual packet of data as it
  arrives at either side of the firewall
• Inbound to or outbound from your computer
• Determines whether it should be allowed to pass
  through or if it should be blocked

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Firewall Rules

• Allow traffic that flows automatically because
  it has been deemed as safe (Ex. Meeting Maker,
  Eudora, etc.)
• Block traffic that is blocked because it has
  been deemed dangerous to your computer
• Ask asks the user whether or not the traffic is
  allowed to pass through

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What a personal firewall can do

• Stop hackers from accessing your computer
• Protects your personal information
• Blocks pop up ads and certain cookies
• Determines which programs can access the Internet

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What a personal firewall cannot do

• Cannot prevent e-mail viruses
• Only an antivirus product with updated
  definitions can prevent e-mail viruses
• After setting it initially, you can forget about
  it
• The firewall will require periodic updates to the
  rulesets and the software itself

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Considerations when using personal firewall
software

• If you did not initialize an action and your
  firewall picks up something, you should most
  likely deny it and investigate it
• Its a learning process (Ex. Spooler Subsystem
  App)
• If you notice you cannot do something you did
  prior to the installation, there is a good chance
  it might be because of your firewall

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Examples of personal firewall software

• ZoneAlarm ltwww.zonelabs.comgt
• BlackICE Defender lthttp//blackice.iss.netgt
• Tiny Personal Firewall ltwww.tinysoftware.comgt
• Norton Personal Firewall ltwww.symantec.comgt

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Windows XP Firewall

• Currently not enabled by default
• Enable under Start -gt Settings -gt Control Panel
• Select Local Area Connection
• Select the Properties button
• Click the Advanced tab

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Windows XP firewall
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Updates to Windows XP Firewall

• Will be enabled in default installations of
  Windows XP Service Pack 2
• Ports will be closed except when they are in use
• Improved user interface for easier configuration
• Improved application compatibility when firewall
  is enabled

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Final Notes

• Rule Management
• Default Allow vs. Default Deny
• Firewalls do NOT Solve the Entire Problem

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