Firewalls

The data in the network is very important for any

organization. Today many organizations face problems with intruder's accessing files on

the work servers. If intruders get into the network and damage the crucial and

confidential files, the consequences would be disastrous. These thoughts always give

sleepless nights to system administrators. Here, firewalls can be attempted as a solution.

What is a firewall





The firewall is a system designed to prevent unauthorized access to or from a private

network. Firewalls can be implemented using either hardware and software, or even a

combination of both. They are frequently used to prevent unauthorized Internet users from

accessing private networks connected to the Internet, especially Intranets. All messages

entering or leaving the Intranet pass through the firewall, which examines each message

and blocks suspicious ones that fail to meet specified security criteria.

Different firewall techniques

Packet filter: Looks at each packet

entering or leaving the network and accepts or rejects it based on the organization’s

security policy. It is fairly effective and transparent to users, but is difficult to

configure and susceptible to IP spoofing (A technique used to gain unauthorized access to

computers, whereby the intruder sends messages to a computer with an IP address indicating

that the message is coming from a trusted port).

Application gateway: Here, security mechanisms are

applied specifically to applications such as FTP (File Transfer Protocol) and Telnet

(Telnet is a terminal emulation program for TCP/IP networks including the most famous of

them all, the Internet. It runs on your PC and connects it to a server on a network)

servers. This is very effective, but can hit performance.

Circuit-level gateway: When a TCP (Transmission

Control Protocol) or UDP (User Datagram Protocol, a connectionless protocol that, like

TCP, runs on top of IP networks) connection is established, security mechanisms are

applied. Once the connection has been made, packets can flow between the hosts without

further checking.

Proxy server: The proxy server effectively hides the

true network addresses.It intercepts all messages entering and leaving the network.

Where is a firewall installed?



Mostly, a firewall is installed in a specially designated computer separate from the rest
of the network so that no incoming request can go directly to the private network

resources. However if you are using a firewall to separate different parts of the same

local network, (e.g. accounts and R&D), the firewall is installed at the perimeter of

the network, ordinarily where it connects to the Internet.

Conclusion



A firewall is no panacea against intrusion into your network. Other routes of attack must
be secured and constant vigil maintained. While trying to protect the critical data behind

the firewalls, care should also be taken to further compartment the networks, making it

harder for the intruder to succeed even after getting into the network. An isolated

network for extra sensitive data would also be a good idea.