Ophcrack is a free open source (GPL licensed) program that cracks Windows passwords by using LM hashes through rainbow tables. The program includes the ability to import the hashes from a variety of formats, including dumping directly from the SAM files of Windows. On most computers, ophcrack can crack most passwords within a few minutes.
Rainbow tables for LM hashes of alphanumeric passwords are provided for free by the developers. By default, ophcrack is bundled with tables that allows it to crack passwords no longer than 14 characters using only alphanumeric characters. Available for freely for download are two Windows XP tables, one small and one fast, and one Windows Vista table.
Objectif Sécurité has even larger tables for purchase, intended for professional use. Larger rainbow tables contain LM hashes of passwords with all printable characters, including symbols and spaces, and are available for purchase.
Ophcrack is also available as Live CD distributions which automate the retrieval, decryption, and cracking of passwords from a Windows system. One Live CD distribution is available for Windows XP and lower, as well as another for Windows Vista and Windows 7. The Live CD distributions of ophcrack are built with SliTaz GNU/Linux.
Starting with version 2.3, Ophcrack also cracks NTLM hashes. This is necessary if the generation of the LM hash is disabled (this is default for Windows Vista), or if the password is longer than 14 characters (in which case the LM hash is not stored).
