- It is a command line tool designed to crack both Unix and NT passwords. John is extremely fast and free
- The resulting passwords are case insensitive and may not represent the real mixed-case password.
John the Ripper is a fast password cracker, currently available for many flavors of UNIX (11 are officially supported), DOS, Win32, BeOS, and OpenVMS. Its primary purpose is to detect weak UNIX passwords. John the Ripper is a part of Owl, Debian GNU/Linux, SuSE, very recent versions of Mandrake Linux, and EnGarde Linux. It is in the ports/packages collections of FreeBSD, NetBSD, and OpenBSD.
John the Ripper is designed to be both powerful and fast. It combines several cracking modes in one program, and is fully configurable for specific needs. As John is available for different platforms, the attacker can use the same cracker everywhere and even continue a cracking session started on a different platform. It supports several cryptographic password hash types most commonly found on various UNIX flavors. Supported out of the box are Kerberos AFS and Windows NT/2000/XP LM hashes, plus several more with contributed patches.
Out of the box, John supports (and auto detects) the following ciphertext formats: standard and double-length DES-based, BSDI's extended DES-based, FreeBSD's MD5-based, and OpenBSD's Blowfish-based. With just one additional command (required to extract the passwords), John can crack AFS passwords and WinNT LM hashes. John has highly optimized modules for different ciphertext formats and architectures. Some of the algorithms used - such as bitslice DES - require a more powerful interface. Additionally, there are assembly routines for several processors and architectures (special Intel Pentium version, x86 with MMX, generic x86, Alpha EV4, SPARC V8).
However, the resulting passwords are case insensitive and may not represent the real mixed-case password. Indeed, this is a small hindrance to a determined patient attacker.
