FireWall is device that provides secure connectivity between networks (internal/external).
A firewall may be a 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.
Software vs. Hardware Firewalls Software Firewall Hardware Firewall
-Protect a single computer
-Usually less expensive, easier to configure
-Protect an entire network.
-Usually more expensive, harder to configure
Norton Internet Security Cisco PIX Mcafee Internet Security NetScreen Outpost WatchGuard Ms. ISA Server Check Point
How does a Firewall work?
Inbound to or outbound from your computer.
Inspects each “ packet ” of data that arrives at either side of the firewall.
Determines whether it should be allowed to pass through or if it should be blocked .
sent sent received received packets packets
How a firewall works ?
An attacker tries to compromise a service on the protected network.
2) The Firewall identifies the attempt .
The FIREWALL can now:
Alert the admin
Harden the firewall
Or reset a TCP/IP connection
LOG Alert Reset Fire Wall
Types of FireWall Techniques
Application gateway (a.k.a. Proxy server)
Packet filter - It looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules . Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing . Packet Filtering Applications Presentations Sessions Transport DataLink Physical DataLink Physical Router Applications Presentations Sessions Transport DataLink Physical Network Network
Application gateway Application gateway (Proxy Server)- User uses TCP/IP applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation. Applications Presentations Sessions Transport DataLink Physical Network DataLink Physical Applications Presentations Sessions Transport DataLink Physical Application Gateway Applications Presentations Sessions Transport Network Network Telnet HTTP FTP
Circuit-level gateway- It is a stand alone application.
It does not permit end-to-end TCP connection. It sets up 2 TCP connections:
> B/w itself and a TCP user on an inner host.
> B/w itself and a TCP user on an outer host.
> Bastion host is a special purpose computer on a network specifically designed and configured to withstand attacks .
> It generally hosts a single application , provides platform for Application gateway and Circuit-level gateway. It supports limited/specific applications to reduce the threat to the computer. Include applications- Telnet,SMTP,FTP.
What a firewall can do ?
What a firewall cannot do ?
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.
Block invalid packets .
What a personal firewall cannot do ?
Cannot prevent e-mail
Only an antivirus product
with updated definitions can
prevent e-mail viruses.
After setting it initially, you cannot forget about it
The firewall will require periodic updates to the rulesets and the software itself.
Virus can jump Firewall !! F I R E W A L L Deadly Virus
SECURED Firewall Thank You…… Source – >CNS Text Book (William Stallings) > Wikipedia