This document discusses different types of firewalls and how they work. It describes hardware and software firewalls, and explains that hardware firewalls protect entire networks while software firewalls protect individual computers. It also outlines different firewall types including packet filters, application-level gateways, circuit-level gateways, and stateful inspection firewalls; and how each works to filter network traffic and protect private networks from unauthorized access.
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E firewalls
1. Firewalls
The function of a strong position is to make
the forces holding it practically unassailable
-On War,(Carl Von Clausewitz)
ABHIROOP GHATAK
en no: 0771184406
29 December 2008 abhiroop@cdac 1
2. 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.
A firewall is simply a program or h/w device that
filters the info.coming through the internet
connection into your private network or
comp-system.IF an incoming packet of info.is
flagged by the filters,it is not allowed through.
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3. 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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4. 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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5. Firewalls denies or permits access based on
rules and policies
Protected Private Network
Internet
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6. 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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7. What a personal firewall can do
Stop hackers from accessing your computer
Protects your personal information
Allow virtual private networks
locks “pop up” ads and certain cookies
Determines which programs can access the
Internet
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8. Firewalls DON’T
Protect against attacks that bypass the
firewall
Dial-out from internal host to an ISP
Protect against internal threats
disgruntled employee
Insider cooperates with and external attacker
Protect against the transfer of virus-infected
programs or files
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9. Type is Firewalls ..
Firewalls fall into four broad categories .
Packet filters
Application level
Circuit level
Stateful inspection firewalls
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11. Packet Filtering Routers
• Forward or discard IP packet according a
set of rules
• Filtering rules are based on fields in the IP
and transport header
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13. Application level gateway
Proxy server
Firewall
Application Proxies
Application Application
Transport Transport
Internal
Network Network Network
Data Link Data Link
Internet
Physical Physical
Router
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14. Continue …
Act as relay of application-level traffic.The
user contacts the gateway using TCP/IP
application,such as FTP ,and the gateway
asks the user for the name of a remote host
to be accessed.When the user responds and
provides a valid user ID and authentication
info. the gateway contacts the application on
the remote host and relays TCP segments
containing the application data between the
two points.
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16. Circuit level gateway(Firewall)
Circuit level gateways work at the session layer of
the OSI model.They monitor TCP handshaking
between packets to determine whether a requested
session is legitimate. Information passed to a
remote computer through a circuit level gateway
appears to have originated from the gateway. This is
useful for hiding information about protected
networks. Circuit level gateways are relatively
inexpensive and have the advantage of hiding
information about the private network they protect.
On the other hand, they do not filter individual
packets.
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18. Continue ..
Whether a connection is valid may for examples be based upon:
destination IP address and/or port
source IP address and/or port
time of day
protocol
user
password
Every session of data exchange is validated and monitored and all
traffic is disallowed unless a session is open.
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19. Stateful inspection firewalls
Firewall/Router
Application - State Table
Transport - Access Rules
Network - Access Rules
Inspection Module
Internal
Network
Network Network
Data Link Router Data Link
Internet
Physical Physical
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20. How to trust firewalls?
Firewalls can be trusted if they provide the
following services
1)Authentication
2)access control
3)data confidentiality
4)data integrity
5)non repudiation
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21. uses of firewalls
Virtual private network
Demiltarised zone
A DMZ can be viewed as a layer of privacy between the corporate
infrastructure and the Internet, exposing only those systems that
must be known to the public.
Ip security
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23. De-militarised zone
Protected private network
Open access
between
private LAN
and DMZ
Allow Internet
SMTP,
From here
to there
WEB only
Server
DMZ
Static filters
Mail between private LAN
Server and DMZ used to
control access
Demilitarised Zone
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24. Ip security
Firewalls are needed when any organization
relies heavily on the internet.
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25. conclusion
Firewall must continue to advance
Firewalls must be developed to scan virus
$377 million (approx.) lost till date
due to network attacks
.
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