Firewalls
Presented by:
Sarah Castro
Karen Correa
Kelley Gates
Fundamentals of Firewalls
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What is a firewall?
– A firewall is a software
or hardware that
prevents unauthorized
access, and enforces an
access control party
between two networks.
– A firewall imposes its
policy on everything
behind it.
– YOU – the user decides
the policy
Why do we need a firewall?
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To prevent certain types of data from
getting in or out of particular areas
Security between the outside world and
your network, especially protection from
most Internet security threats
Firewalls keep damage on one part of the
network
What does a firewall protect against?
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Security threats
posed by the Internet
Unauthenticated
interactive logins
Application
backdoors
SMTP session
hijacking
Operating system
bugs
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Denial of service
E-mail bombs
Macros
Viruses
Spam
Redirect bombs
Source routing
What does a firewall not protect
against?
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Certain class of threats such as inside attacks,
and Outside attacks that it cannot detect
Tunneling over most application protocols to
trojaned or poorly written clients
Data-driven attacks- something is mailed or
copied to an internal host where it is then
executed.
–
Past occurrences against OutLook
OSI MODEL & FIREWALLS
Packet Filter Firewalls
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Work at network layer
Usually routers and firewall appliances
Scan IP header in rule base for:
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Source IP address
Destination IP address
TCP/UDP source port
TCP/UDP destination port
Example on web
Circuit Level Gateways
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Work in session layer of the OSI model (~
transport layer of the TCP/IP model)
Ensures that the session between two end
users is legitimate
However, no further processing or filtering of
individual packets is done.
Application Level Gateways
Work in application layer
 Usually proxy servers, also personal
firewalls
 High level of security
 Can slow down network
 Example: Proxy Server and DMZ
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Stateful Multilayer Inspection Firewalls
Combination of the above
 High level of security, and good
performance
 Expensive
 Complex
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TYPES OF FIREWALLS
Personal Firewalls
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Software-only solutions
No external devices
– Easy to install and upgrade
Protects against:
– Worms, Trojan horses, and spyware
Examples: ZoneAlarm, BlackIce
Advantages, Disadvantages
Firewall Appliances
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Specialized hardware devices, sometimes
part of SOHO router
Can be Plug and Play
Provide NAT and TCP port inspection
DMZ
Example: NetGear, Linksys etc.
Turnkey Solutions
Turnkey solutions combine (arguably)
the best of both Appliance and
Software-only solutions
 Wider range of services offered
 More expensive, greater number of
components
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Differences between software and
hardware firewalls
On webpage:
 Level of Protection
 Manageability
 Cost Analysis
 Feature Set Comparison
 Future Outlook
 Grade Summary
REMEMBER
 The
use of firewalls presents a
tradeoff between service and
protection.
 Decide what your optimal balance
between security and service is!!!
Conclusion
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Implementing a firewall is a great tool
for security purposes
BUT, DO EXPECT FAILURE
PLAN FOR THE WORST
Q&A
Questions?