John the Ripper is a password cracker, currently available for UNIX, DOS,
WinNT/Win95. Its primary purpose is to detect weak UNIX passwords. It has
been tested with Linux x86/Alpha/SPARC, FreeBSD x86, OpenBSD x86, Solaris
2.x SPARC and x86, Digital UNIX, AIX, HP-UX, and IRIX.

The DOS and Win32 ports are done with DJGPP and Cygnus Developer's Kit,
respectively.