Password Cracking: For lab 8 you will examine password cracking.
Password strength is the measure of a password’s efficiency to resist password cracking attacks. The strength of a password is determined by;
Let’s now look at a practical example. We will use three passwords namely
For this example, we will use the password strength indicator of Cpanel when creating passwords. The images below show the password strengths of each of the above-listed passwords.
This is a trial service and will work for you to look at the passwords.
The higher the strength number, better the password.
Let’s suppose that we have to store our above passwords using md5 encryption.
The table below shows the password hashes.
|Password||MD5 Hash||Cpanel Strength Indicator|
We will now use http://www.md5this.com/ to crack the above hashes. The images below show the password cracking results for the above passwords.
As you can see from the above results, we managed to crack the first and second passwords that had lower strength numbers. We didn’t manage to crack the third password which was longer, complex and unpredictable. It had a higher strength number.
Password cracking techniques
There are a number of techniques that can be used to crack passwords. We will describe the most commonly used ones below;
Spidering sample dictionary attack wordlist
1976 <founder birth year>
smith jones <founder name>
acme <company name/initials>
built|to|last <words in company vision/mission>
golfing|chess|soccer <founders hobbies
Examine the available software for Kali Linux.
John the Ripper
John the Ripper uses the command prompt to crack passwords. This makes it suitable for advanced users who are comfortable working with commands. It uses to wordlist to crack passwords. The program is free, but the word list has to be bought. It has free alternative word lists that you can use. Visit the product website https://www.openwall.com/john/ for more information and how to use it.
Cain & Abel
Cain & Abel runs on windows. It is used to recover passwords for user accounts, recovery of Microsoft Access passwords; networking sniffing, etc. Unlike John the Ripper, Cain & Abel uses a graphic user interface. It is very common among newbies and script kiddies because of its simplicity of use. Visit the product website http://www.softpedia.com/get/Security/Decrypting-Decoding/Cain-and-Abel.shtml for more information and how to use it.
Ophcrack is a cross-platform Windows password cracker that uses rainbow tables to crack passwords. It runs on Windows, Linux and Mac OS. It also has a module for brute force attacks among other features. Visit the product website http://ophcrack.sourceforge.net/ for more information and how to use it.
In this practical scenario, we are going to crack Windows account with a simple password. Windows uses NTLM hashes to encrypt passwords. We will use the NTLM cracker tool in Cain and Abel to do that.
Cain and Abel cracker can be used to crack passwords using;
We will use the dictionary attack in this example. You will need to download the dictionary attack wordlist here 10k-Most-Common.zip.
For your exercise, create a few accounts on both Linux and Windows VMs. Using the most common passwords, use Cane and Abel to attempts cracks on the passwords of varying size and difficulty. Also, think about changing the common passwords to see the difference in time. Record your finding