Windows: How To Crack Passwords

By: Darren Miller

Cracking Passwords

One of the key components in performing a security assessment is the acquisition of user account information and cracking of the account password. There are many methods and tools that can be used to crack passwords, however, you must first retrieve the information to crack. And once again, there are many ways of acquiring the account information. This article will illustrate one method of acquiring user account information using a combination of social engineering and open source tools. We will then briefly go over a particular cracking method and tool.

Handing Over The Keys To The Kingdom

On one particular occasion, we were instructed by a client to do what ever it took, within legal means, to walk out of their building with the network user account information.

We were introduced to one of the Sr. Engineering staff as a consultant working on a new Anti-Virus solution. We asked the Engineer to show us around the server room and he happily did so. While we were talking, we asked him if he would mind if we ran a specialized virus checker on one of the Windows domain controllers, and he readily provided us with console access.

The disk we were using was labeled to look like it contained anti-virus tools. In reality, it contained a modified version of a program called "pwdump". The moment we ran the script, a bunch of information came up that indicated that their systems memory was clear of any known virus. What was really happening was all domain account information and the corresponding password hashes were being dumped to a file on the disk. We rapped up our tour and walked out of the building with everything we needed.

Windows Password Cracking

When we returned to our office, we imported all the user account information in a distributed password cracking system (Multiple servers performing password cracking at the same time). Within approximately 30 minutes we had cracked 70% of account passwords. The remaining accounts took approximately two days.

An example of what this Windows account information looks like is:

jdoe:1152:A5C67174B2A219D1

The jdoe accounts password is represented by its hashed equivalent "A5C67174B2A219D1". This string of number and letters, when deciphered, is "CrackMe". You can test this with the tool I am going to introduce you tool in the next section of this article. Without going into all the technical details about how the cracking takes place, this type of deciphering is basically done by trying to match up the hashed password over time and a bunch of iterations. When you take the word "CrackMe", and hash it, it produces the string of numbers and letters (A5C67174B2A219D1). So what you are really doing is matching that string, then making the assumption that the human readable version is "CrackMe".

How To Generate Password Hashes

First and foremost I must warn you that the tool I am going to point you to is very powerful and could cause you problems if you are not careful with it. You must agree to hold me harmless if in fact you decide to download and use this tool. This tool, called Cain & Abel, is the Swiss Army knife of cracking and does a lot more than just that.

Once it is installed on your system, you can go to the "Tools" menu and choose "Hash Calculator". In the "Text to Hash" box type "CrackMe" without the ""'s and hit calculate. Look at the Type "LM" and you will see the hash from above of ":A5C67174B2A219D1".

This tool as a great password cracking program and we use it quite regularly. And as I said, it does a lot more than just cracking so be careful with it.

Conclusion

As I stated in the beginning of this article, there are many ways to obtain account information and many more ways to decipher it. In this case, we physically walked out of an office building with everything we needed. Shortly after cracking all the accounts we were able to use their remote access system to gain entry into their internal network as an administrator. There are also ways of capturing user account information using man-in-the-middle attack techniques, remote social engineering, and phishing just to name a few.

The bottom line is, make your passwords complex, and change them as often as you can.