PassWord Cracking

Information is a Precious resource. It needs to be accessed and shared with legitimate people. Towards that end, access to information is usually protected via the use of authentication systems.A promgram is used that algorithms that guess passwords.

What is password strength?
Password strength is the measure of a password’s efficiency to resist password cracking attacks. The strength of a password is determined by;

• Length: the number of characters the password contains.
• Complexity: does it use a combination of letters, numbers and symbol?
• Unpredictability: is it something that can be guessed easily by an attacker?

three passwords with different strenghts :
    1. password
    2. password1
    3. #password1$
What Cracking a Hash of encrypted Passwords for One of many times of Hash
                                   Examples Below :

• Note: the password used is password the strength is 1 and it’s very weak.
• Note: the password used is password1 the strength is 28 and it’s still weak.
• Note: The password used is #password1$ the strength is 60 and it’s strong.
• The higher the strength number, better the password.

 md5 encryption(One of the many different types of hash). We will use an onlinemd5convertor to convert our passwords into md5 hashes.
 password hashes:
Password
MD5 Hash

               Password  |              MD5 Hash      Cpanel Strength Indicator

1. Hash for : Password : 5f4dcc3b5aa765d61d8327deb882cf99 (Level 1)
2. 1. Hash for : Password1 : 7c6a180b36896a0a8c02787eeafb0e4c (Level 28)
3. Hash for : #password1$ : 7c6a180b36896a0a8c02787eeafb0e4c(Level 60)
YOy will now use http://www.md5this.com/ to crack the above hashes.

Password cracking techniques
There are a number of techniques that can be used to crack passwords.

• Dictionary attack– This method involves the use of a wordlist to compare against user passwords.
• Brute force attack– This method is similar to the dictionary attack. Brute force attacks use algorithms that combine alpha-numeric characters and symbols to come up with passwords for the attack. For example, a password of the value “password” can also be tried as p@$$word using the brute force attack.
• Rainbow table attack– This method uses pre-computed hashes. Let’s assume that we have database which stores passwords as md5 hashes. We can create another database that has md5 hashes of commonly used passwords. We can then compare the password hash we have against the stored hashes in the database. If a match is found then we have the password.
• Guess– As the name suggests, this method involves guessing. Passwords such as qwerty, password, admin etc. are commonly used or set as default passwords. If they have not been changed or if the user is careless when selecting passwords, then they can be easily compromised.
• Spidering– Most organizations use passwords that contain company information. This information can be found on company websites, social media such as facebook, twitter etc. Spidering gathers information from these sources to come up with word lists. The word list is then used to perform dictionary and brute force attacks.

Spidering sample dictionary attack wordlist

1. 1976
2. smith jones
3. acme
4. built|to|last
5. golfing|chess|soccer <founders hobbies>

Password cracking tool
These are software programs that are used to crack user passwords. We already looked at a similar tool in the above example on password strengths. The website www.md5this.com uses a rainbow table to crack passwords.
commonly used tools :
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 wordlists that you can use. Visit the product websitehttp://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 websitehttp://www.oxid.it/cain.html for more information and how to use it.
Ophcrack
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.
Password Cracking Counter Measure
An organization can use the following methods to reduce the chances of the passwords been cracked 

1. Avoid short and easily predicable passwords
2. Avoid using passwords with predictable patterns such as 11552266.
3. Passwords stored in the database must always be encrypted. For md5 encryptions, its better to salt the password hashes before storing them. Salting involves adding some word to the provided password before creating the hash.
4. Most registration system have password strength indicators, organizations must adopt policies that favor high password strength numbers. 
    

Summary
Password cracking is the art of recovering stored or transmitted passwords.
Password strength is determined by the length, complexity and unpredictability of a password value.
Common password techniques include dictionary attacks, brute force, rainbow tables, spidering and cracking.
Password cracking tools simplify the process of cracking passwords.