What is John The Ripper?

John The Ripper is perhaps the best known password cracking (hacking) tools out there, and that’s why it will always be in our ‘concise top ten hacking tools’ category.
Aside from having the best possible name, we love John, as it is affectionately known, because simply said, it works and is highly effective.
John The Ripper is, like Metasploit, also part of the Rapid7 family of pentesting/ hacking tools.

How do Password Crackers Work?

In cryptanalysis, (which is the study of cryptographic systems in order to attempt to understand how it operates, and, as hackers, we’ll try to see if there are any vulnerabilities that will allow them to be broken, with or without the hash/ password key). Password cracking is the process of recovering or hacking passwords from data that have been stored in or has been transmitted by a computer system or within a network.
One of the most common types of password hacking is known as a ‘brute-force attack.’ which, simply said, is the process in which a computer system guesses for the correct by cross-checking against an available cryptographic hash of the password.
If the brute force attack is against clear-text words then the process derives from a ‘dictionary attack’.
If the password is guessed using password hashes (which is faster), then the used process would be a ‘rainbow’ table.

If you work in Cyber Security, or are looking to get started in the profession, then it is ‘a must’ that you learn certain aspects of cryptography.
We’d therefore strongly suggest that you learn, and try to crack, offline passwords using John The Ripper.

How does John The Ripper compare to THC Hydra?

THC Hydra, or simply ‘Hydra’, is another very popular password hacking tool that is often referred to in the same context as John The Ripper.
The easiest way to describe the difference between John The Ripper (JTR) and THC Hydra is that JTR is an offline password cracker whilst Hydra is an online password cracker.

Is John The Ripper Free?

Both. There is a very popular free version of John The Ripper, and also a ‘pro’ version.
John the Ripper commerical version is used by penetration testers that are interested in password cracking specific operating systems.
The commercial version optimized for performance and speed.
For the average user John The Ripper ‘open-source’ will work great, for the real hard-core user we’d certainly recommend the Pro Version, available from Rapid7.

Does John The Ripper Work on all Operating Systems?

John The Ripper was originally developed for Unix operating systems but now runs on various platforms 11 of which are architecture-specific versions of DOS, Unix, BeOS, Win32 and OpenVMS.

What are Typical Uses for John The Ripper?

John the Ripper is a fast password cracker. Period.
In fact, you can consider John The Ripper as ‘the definitive’ password hacking tool!

Link : http://www.openwall.com/john/

Source : https://www.concise-courses.com/hacking-tools/password-crackers/john-the-ripper/