Lab: John the Ripper.

Step1: Setup

• Install the virtual machine John.ova.
• Log in as bob, password bob.
• Install John the ripper
  • sudo apt install john
  • This will install the software John the Ripper and the associated data files.
• Grab a word list or two (just click to download)
  • lower.gz
  • Note, these are part of the john project. You can read about them here.
    • You just downloaded the one of the English/small files.
    • There are much more extensive files available.
    • We have limited the download to make our examples work more quickly.
• Make a directory to work in (I called mine john)
  • Change to john and copy the downloaded wordlist there.
  • cp ~/Downloads/lower.gz .
  • gunzip lower.gz
• While you are working, you might want access to the Documentation for john.

Step2: Background

• John the Ripper is an extensive set of tools for cracking passwords.
  • While this may or may not be useful to you when protecting a system
  • It is vital that you understand that this tool exists and that it can be used against your systems.
• John operates in at least four modes
  • Using the information stored in the password file, attempt to crack the passwords by guessing.
  • Using a built on the fly rainbow table, check for cracked passwords.
  • Use a default list of words try all of these words.
  • Use a default list of rules, try all mutations of the words given.
  • Try a brute force attack.
• You can, if you wish, supply other lists including words and rules.
• John can run in parallel, easily using all the processors on a system.
• John is configured to run as a long term process
  • It saves checkpoints so it can be restarted.
  • It saves work completed as a checkpoint.
• All in all John is a very sophisticated tool, which we will explore in the next section.