Password cracking

1
Password cracking

• Patrick Sparrow, Matt Prestifillipo, Bill
  Kazmierski

2
Overview

• Who uses password crackers?
• List of programs needed
• Gain access to password list
• Password Salting
• Installing John the Ripper
• How to use PwDump2 and John the Ripper
• How to make a strong password

3
Who uses password crackers?

• System Administrators
• Test the strength of the users password
• Hackers
• Gain access to the users account

4
List of programs needed

• Pwdump2
• Retrieves user accounts and passwords in Windows
  and puts the information into a hash table (not
  needed in Unix)
• John the Ripper
• Uses hash table from pwdump2 and cracks password

5
John the Ripper cont.

• Runs against various encrypted password formats
  including Unix (based on DES, MD5, or Blowfish),
  Kerberos AFS, and Windows NT/2000/XP/2003 LM hash
  
• It operates by the so-called dictionary attack.
  It takes text string samples (usually from a file
  containing words found in a dictionary),
  encrypting it in the same format as the password
  being examined, and comparing the output to the
  encrypted string.
• It also can operate by the incremental attack.
  Where JTR tries every possible character
  combination as passwords.
• Several thousand possibilities can be tried per
  second
• Most sufficient way of cracking passwords in the
  past several decades

6
Gain Password List

• Windows
• Use Pwdump2 to get SAM file when logged into
  account
• Use a Live Bootable OS CD (Knoppix) to by-pass
  user login and change directory to the Windows
  SAM File and dump to disk
• Unix
• Unshadow password in /etc/passwd
• ./unshadow /etc/passwd /etc/master.passwd gt
  pass.txt
• ypcat passwd when NIS is used
• Use Live Bootable OS CD (Knoppix)

7
Password Salting

• Salts help strengthen the password list
• The salt is suffixed with random values to the
  password before encrypting it the salt is stored
  along with the encrypted password in the hash
• Salts are different for each user, the attacker
  can no longer use a single encrypted version of
  each candidate password.
• Makes for longer time of cracking passwords
• More difficult for dictionary attack

8
Installing Pwdump2 and JTR

• Simply extract both programs to separate
  directories, no install needed for Windows
• For Unix
• CD to ./src of the JTR dir after extraction.
• make
• make clean generic

9
How to use Pwdump2 and JTR
10
How to make a strong password

• Do not use single dictionary words
• Use a combination of words with a punctuation
  mark in between each word, along with a mix of
  upper and lower case letters for each word