Securing Linux: A Survival Guide for Linux Security (Version 2.0)

4.4 JOHN THE RIPPER

John the Ripper is a freeware password auditing utility or, as some like to call it, a password cracking utility. John the Ripper attempts to brute force guess the passwords in the passwd and shadow files, making use of dictionaries and its knowledge of common password creation techniques. John the Ripper has three modes in which it will run:

• Single Crack Mode “ Uses the login and GECOS (Full Name , home directory, etc) information from the passwd file as its password word list.

• Wordlist Mode “ Uses a populated wordlist or dictionary list.

• Incremental Mode “ Uses all combinations of characters . This is sometimes known as brute force mode.

John the Ripper can be obtained at http://www.openwall.com/john/.