Transcript Firewalls

Firewalls
Network Security
Marshall Leitem
11/30/04
Overview
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What is a firewall?
What does it protect us from?
What does it consist of?
Hardware/software
Questions?
What is a Firewall?
 fire·wall
Any of a number of security schemes that
prevent unauthorized users from gaining
access to a computer network or that
monitor transfers of information to and
from the network.
Securities Employed
 Packet Filtering
Checks incoming packets to see they meet set requirements, if
not the packets are discarded.
 Proxy Service
Information from the Internet is retrieved by the firewall and
then sent to the requesting system and vice versa.
 Stateful inspection - doesn't examine the contents of each
packet, compares certain key parts of the packet to a database
of trusted information. Information traveling from inside the
firewall to the outside is monitored for specific defining
characteristics, then incoming information is compared to
these characteristics. If the comparison yields a reasonable
match, the information is allowed through. Otherwise it is
discarded
What does it consist of?
 Software Implementations
 Zone Alarm
 Omniquad Personal Firewall
 Norton Personal Firewall
 Hardware Implementations
 Linksys Etherfast Cable/DSL Firewall Router
 CISCO PIX 500 Firewall
Pictures
Basic Topology
Examples of Common
Filters
 IP Address – has the ability to block
specific IP’s or Domains or only permit
specific ones.
 Domains – can block access to specific
domains or only allow specific domains
 Protocols
 Ports
 Key Words
What it Prevents
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Remote Login
Application Backdoors
SMTP session Jacking
Denial of Service Attacks
Spam
Source Routing
Demilitarized Zone
 You want the un-trusted or un-known
networks to have access to some of your
resources
 You still want to maintain a secure
private network
 A Firewall is used to create this area
DMZ(demilitarized zone)
DMZ
Downside of Firewalls
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Performance Degradation
Can be difficult to configure
Can be susceptible to IP-Spoofing
Can Interfere with some software
Extra Costs
Benefits of Firewalls
 Provides a “choke point” in which traffic
can be evaluated to see it meets
specifications.
 Prevents Remote Login
 Allows rules on users and data traveling
through to be imposed.
What can’t Firewalls Protect
Against?
(Steel door on a Wooden House)
 Attacks that don’t go through firewall
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Traitors
Manually Moving of Data (tape storage, etc)
Tunneling
Trojans & Viruses
Cost Options?
 Free – software based firewalls can be
found
 Exspensive up to $100,000+ hardware
solutions that require much time and
effort to install
Hardware Vs. Software
 Hardware
 in most cases, they can be effective with
little or no configuration
 can protect every machine on a local
network
 Can be susceptible to attacks from inside
the private network due to trojans
 Often packet filtering is set up too trusting of
outgoing packets
 Group wide Policy
Hardware Vs. Software
 Software
 you can specify which applications are allowed
to communicate over the Internet from that PC
(ex: only outlook express can use Port 25)
 can only protect the machine they're installed
on
 Better protection against trojans and worms
than hardware but must be configured on each
machine
Questions?