Firewall
Ercan Sancar
&
Caner Sahin
Index
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History of Firewall
Why Do You Need A Firewall
Working Principle Of Firewalls
Can a Firewall Really Protect Me?
Multiple Firewalls
Firewall Functions in Windows
Choosing a Firewall that Meets
History Of Firewall
Firewall technology emerged in the late
1980s...
Why Do you Need a Firewall?
What is Firewall???
• A firewall is a piece of software or
hardware...
What Firewall Do???
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Block incoming network traffic based on source or destination.
Block outgoing network traffic based on source or destination.
Block incoming network traffic based on content.
Make internal resources available.
Allow connections to internal network.
Report on network traffic and firewall activities.
What Firewall Can’t Do???
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Inside attack!
Social engineering.
Viruses and Trojan horse programs.
Poorly trained firewall administrators.
A Firewall That Fits
• Personal Firewall
• Departmental or small organiztion Firewall
• Enterprise Firewall
Some Firewall Rules
• Allow everyone to access all Web Sites
• Allow outgoing e-mail from the internal mail server
• Drop all outgoing network traffic unless it mathces the first
two rules
• Allow incoming Web request to the public Web server
• Drop all incoming network traffic expect for connections
to the public Web server
• Log all connection attempts that were rejected by the
firewall
• Log all access to external Web sites
Basic Function of Firewall
• Packet filtering
• Network Address Translation(NAT)
• Application Proxy
Working Principle of Firewalls
• General Strategy: Allow-All or Deny-All
• Filtering Properties
General Strategy of Firewall
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Allow-all Strategy:Allow all network packets except those
that are explicitly denied.
Deny-all Strategy:Denies all network packets except those
that are explicity allowed.
Example Firewall Rules
Filetering Properties
• Packet Filtering
• Network Address Translation(NAT)
• Application Proxy
Packet Filtering
• What is Packet Filtering?
• Filtering IP data.
Example of Fragment
Network Address
Translation(NAT)
• What is NAT?
• Security Aspects of NAT.
• Consequences of NAT.
Application Proxy
• What is Application Proxy
• Differnce between Application Proxy and
Packet Filtering
• Advantages of Application Proxy
• Drawbacks of Application Proxy
Comparison of NAT & Proxy
NAT
• Network and
Transport layer
• Not concerns with
contents
• Users don’t need any
settings
• Every program uses
the same
Proxy
• Application Layer
• Interface with the
content
• Users need to setup
the settings
• Differnt programs can
use differnt proxies
Can a Firewall Really Protect
Me?
A firewall is indeed a very effective
method of protection against many of these
threats, but...
Multiple Firewall
• When Two Firewall Are Better Than One
• Designing Demilitarized Zones(DMZ)
Designing Demilitarized Zones
Advantages of DMZ with Two
Firewall
• Clear Definition of The DMZ
• Increased Security
• Reduce Network Loads on the Two Firewalls
Disadvantages of DMZ with Two
Firewall
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Increased Cost
Extra Training Required
Multiple Firewall Rule Listing Must be Maintained
Configuration Complexity When more Than Two
Firewall are Deployed
Firewall Functions in Windows
• Packet Filtering
• Network Address Translation(NAT/ICS)
• Encrypted Tunnel
Firewall Functions Which is not
provide in Windows
• No application Proxies
• No (or less-than-ideal)monitoring and logging
• No data caching
Choosing a Firewall That Meets
• How do you decided?
• What compare?
Thank you For Listening