Pierluigi Paganini October 14, 2013

The Hacker Academy provides a unique learning experience, teaching infosec from the hacker’s perspective.

Password cracking is one of the most popular methods used to gain unauthorized access to a computer system. Using cracking to Obtain password hashes is something you can do with physical or remote access to a system.

John the Ripper is one of the best password testing and breaking tools. So, how’s it work? It combines a number of password crackers into one package, detects different password hash types, and matches that with a customizable cracker.

John the Ripper is mostly used during penetration tests in cracking NTLM passwords for domain credentials we have dumped from a Windows Domain Controller that is storing LM hashes. Cracking the LM password hashes can be done for all accounts using rainbow tables in less than an hour. We can’t use these LM cracked passwords to authenticate to other hosts/servers, but we can use them as a wordlist to crack the NTLM passwords for all domain users in just a few minutes using the built in NT rule for John the Ripper.

Everyone likes free, and the great thing about John the Ripper is it’s just that. It’s Open Source and available for everyone to use, distributed primarily in source code form.

Jeremy Conway, Instructor at The Hacker Academy, says the following about John the Ripper, “During one of our recent penetration tests, we cracked just over 3,000 accounts in about 2 hours. These credentials led us to compromising other devices and servers that were not part of the domain due to password reuse. Getting credentials is one of the fastest ways for us to gain complete and total control of a targeted network and can be extremely difficult for a company defender to detect and mitigate.”

The Hacker Academy has recognized the importance and accessibility of John the Ripper and dedicated an entire module to introducing members to cracking passwords using password hashes and John the Ripper. Check out this short, clip introducing you to the tool. For a more in depth lesson, click here to sign up for a free trial. This lesson has been opened up strictly for the readers of this blog! Once you’ve accessed the demo account, you’ll be able to find the full video Password Cracking: John the Ripper in the Penetration Testing course under the Server Pen Testing Lesson. Enjoy!

View the full video here!