# it-e-12 What is a Firewall

The term "firewall" illustrates a system that protects a network and the machines on them
from various types of attack. Firewalls are geared towards keeping the server up all the time and
protecting the entire network.
The primary goal of a firewall is to implement a desired security policy; controlling access
in both directions through the firewall, and to protect the firewall itself from compromise. It
wards off intrusionattempts, Trojans and other malicious attacks.
They are meant for the home user in a networked environment. They aim to block simple
attacks, unlike the enterprise level firewalls that the corporate world uses at the server or router end.
There are many ways to implement a firewall, each with specific advantages and disadvantages.
Nowadays organizations and professionals use Internet technology to establish their online
presence and showcase their products and services globally. Their endeavor is to leverage digital
technology to make their business work for them.
All the organizations and professionals are shifting from Dialup to broadband and getting a
fixed IP. It has led to an increase in security attacks, bugs in everyday working. This does not

mean that Dialup being anonymous dynamic link or the firewall of the ISP network make you
pretty safe.
Now if your machine was under attack, you must have wondered what went wrong making
your system crash suddenly. It is not necessary for anyone to actually know about you or your IP
If your system is infected or prone to intrusions, then beyond the anonymity of your Dialup
connection or a dynamic IP, your system can be hacked.
Intrusion

There are many ways to gain unauthorized access to a system. Operating system
vulnerabilities, cracked or guessed passwords are some of the more common. Once access is
attained, the intruder can send email, tamper with data, or use the system privileges to attack
another system.
Information Theft and Tampering

Data theft and tampering do not always require that the
system be compromised. There have been many bugs with FTP servers that allow attackers to
A Service Attacks

Any attack that keeps the intended user from being able to use the
services provided by their servers is considered a denial of service attack. There are many types
of denial of service attacks, and unfortunately are very difficult to defend against. "Mail bombs"
are one example in which an attacker repeatedly sends large mail files in the attempt at filling the
server's disk file system thus preventing legitimate mail from being received.
Joyrider

Not all attacks on computer systems are malicious. Joyriders are just looking for
fun. Your system may be broken into just because it was easy, or to use the machine as a
platform to attack others. It may be difficult to detect intrusion on a system that is used for this
purpose. If the log files are modified, and if everything appears to be working, you may never
know.
Vandals

A vandal is malicious. They break in to delete files or crash computer systems
either because they don't like you, or because they enjoy destroying things. If a vandal breaks
into your computer, you will know about it right away. Vandals may also steal secrets and target
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