It can run against various encrypted password formats including several crypt password hash types commonly found in Linux, Windows. It can also be crack password of Compressed files like ZIP and also Documents files like PDF.
John the Ripper works in 3 distinct modes to crack the passwords,
- Single crack mode
- Wordlist crack mode
- Incremental mode
Single crack mode:
In this mode John the ripper will make use of available information to it in the form of username and other information. This can be used to crack the password files with the format of Username: Password.
For Ex: If the username is "Hacker" it would try following passwords,
Hacker
H-acker
hacKer
hackeR=
Syntax: john [mode/option] [passwordfile]
Wordlist crack mode:
In this mode John the ripper uses wordlist that can also be called as Dictionary. It compares the hashes of the words present in the Dictionary with the password hash.