John the Ripper is often used in the enterprise to detect weak passwords that could put network security at risk, as well as other administrative purposes. The software can run a wide variety of password-cracking techniques against the various user accounts on each operating system and can be scripted to run locally or remotely.
Originally developed for Unix-derived systems, John the Ripper is available for most common platforms. The free and open source (FOSS) version is generally distributed as source code. A commercial version, John the Ripper Pro, is a more user-friendly version distributed as native code for a given system.