John The Ripper (JTR) is one of best password cracker ever built. At the first time, it’s design to detect the weakness of UNIX password. Now, it’s available for Unix, Linux, Windows, DOS, BeOS and Open-VMS. It supports several crypt password hash types in Unix, Kerberos AFS and windows NT/2000/XP LM hashes.
John The Ripper is a free and open source and distributed in source code file but for easy installation you can buy John The Ripper Pro.
Before we start, you have to download JTR from http://www.openwall.com/john/g/john-1.7.9.tar.gz and put it in your selected folder.
In this tutorial, I put JTR under /opt folder.
Type ‘sudo tar xvzf‘ following by JTR file name. The name can be different depend on which version that you have. I type: sudo tar xvzf john-1.7.9.tar.gz