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CIS 450 – Network Security

This article explores the mechanisms behind UNIX password crackers, emphasizing the importance of identifying weak passwords in UNIX environments. It explains how UNIX stores passwords, utilizing files like /etc/passwd (non-sensitive information) and /etc/shadow (hashed passwords). The discussion includes various password cracking tools such as John the Ripper and Slurpie, highlighting their features and capabilities. Additionally, it provides strategies for protecting against these threats, including a strong password policy, the use of shadow files, one-time passwords, and biometric authentication to enhance security.

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CIS 450 – Network Security

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  1. CIS 450 – Network Security Chapter 10 – UNIX Password Crackers

  2. Easiest way to identify weak passwords in a UNIX environment is to utilize UNIX password cracker tools • Where are Passwords stored in UNIX? • Non-sensitive information in /etc/passwd, which is world readable • The hashed passwords stored in /etc/shadow with only those with root access can read the shadow file

  3. How Does UNIX Encrypt Passwords • Uses an encryption algorithm called Crypt to encrypt its passwords • http://fooassociates.com/phpfer/html/rn58re1161.html • Uses DES, Blowfish,and MD5 algorithms

  4. UNIX Password Cracking Programs • Master List • http://neworder.box.sk/box.php3?gfx=neworder&prj=neworder&key=passhack&txt=Unix%20password%20crackers • Crack • http://www.crypticide.com/users/alecm/security/c50a.txt • John the Ripper • http://www.openwall.com/john/ • XIT • http://neworder.box.sk/codebox.search.php?srch=xit • Slurpie • Similar to John The Ripper and Crack except it is designed to run on multiple computers simultaneously, creating a distributed password cracking attack. • http://www.ussrback.com/distributed.htm

  5. Protecting Against UNIX Password Crackers • Have a strong password policy – pages 377 - 378 • Use shadow files – page 378 • Use one-time passwords – passwords change every time use logs on – page 379 • Use biometric authentication – authenticates a user based on human factors – page 380 • Use UNIX Password Programs to enforce strong passwords • General information – page 380 • http://www.foobargeek.com/docs/epasswd.html • Passwd+ • http://www.securityfocus.com/tools/1065 • Npasswd • http://www.utexas.edu/cc/unix/software/npasswd/doc/ • Epasswd • http://www.nas.nasa.gov/Groups/Security/epasswd/

  6. Protecting Against UNIX Password Crackers • Audit access to key files – normally only way to detect the attack is to catch them when the password or shadow file is being accessed - page 381 • Scan for cracking tools – page 381 • Keep inventory of active accounts – company should have a policy for checking active accounts & removing accounts that are no longer active – page 381 • Limit who has access to root – page 382

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