All operating systems that connect to the internet use a hosts file. This file in the windows environment can be found in the directory that contains the windows operating system i.e. WINDOWS or WINNT. you can use the find command in the windows explorer to find your copy if one exists on your computer.

The hosts file is a hangover from the days when the internet was young. Before we had the domain naming system we needed to be able to make a connection between the name of a computer and the IP address that is used to make the actual connections. The hosts file is a text file that contains the name of the computer followed by the IP address of the computer on the same line.

The reason the hosts file is important is that the TCP protocol still checks for a hosts file, and uses it first. If an intruder can get a hosts file onto your computer he can redirect any domain name to an IP address of his choice. This is transparent to you as the user, so you think you are going to the correct address.

#Sample Hosts File

127.0.0.1 Localhost
192.168.44.81 www.google.com
192.168.44.82 internetbanking.suntrust.com

This sample file if it is installed on your computer would connect every attempt to use google with a connection to the attackers' computer, and every attempt to use the internet banking at SunTrust with the intruders' computer.