(JohntheRipper is a UNIX password cracking tool. The working system environment that can be used is unix (tested on linuxx86, FreeBSDx86, Solaris2.xSPARC, OSF/1Alpha), DOS, WinNT/Win95. Of course, before you use John, the most Jia has used other unix password cracking tools, so you can easily understand how John works and how to operate!)