Re: Password hashes

From: Carey Frisch [MVP] (cnfrisch_at_nospamgmail.com)
Date: 10/30/05 

Date: Sat, 29 Oct 2005 17:43:42 -0500

How to prevent Windows from storing a LAN manager hash of your
password in Active Directory and local SAM databases
http://support.microsoft.com/default.aspx?scid=KB;EN-US;q299656& 

-- 
Carey Frisch
Microsoft MVP
Windows - Shell/User
Microsoft Community Newsgroups
news://msnews.microsoft.com/
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"Lawson Poling, MCSA" wrote:
| After reading some security articles about making passwords and 
| authentications more secure on a Windows Server 2003 domain, I was surprised 
| to learn that storing LM hashes is turned on by default, and that it is 
| broken up into two 7 character units. That would explain why, when using 
| L0ftcrack to audit user passwords with 8 characters, that the last character 
| was always found so easily. It places only one character in the second hash. 
| So much for the idealistic minimum 8 character passwords.
| I also learned that the NTLM hash was a single 14 character hash, but it's 
| still as vulnerable at the LM hash. It would just take longer to crack a 
| solid 14 character password.
| I thought I'd get clever and  I made my password 15 characters long. 
| L0ftCrack was no longer able to recognize it. It marked my user account under 
| the LM column as *empty* and won't even try to crack it. I got all warm and 
| fuzzy and was feeling good about myself until I learned about Rainbow Crack. 
| My understanding about it is that it's hash tables only go to 14 characters 
| because the storage space required to store hashes up to 15 characters take 
| too much storage space. If that's true, then it would have to resort to brute 
| force which I imagine would take a very long time to crack a 15 character 
| password. I should say pass-phrase at this point. I don't know too many 15 
| character words. I'm not that smart...
| So this leads me to my penultimate question(s): Does a 15 character 
| pass-phrase automatically get stored in an NTMLv2 hash? It certainly won't 
| fit into a LM or NTLM hash.
| Isn't an NTLMv2 hash good for up to 128 characters? If this is true, then 
| how come when I try to set the minimum password length in the default domain 
| policy that I can only toggle it up to 14 characters?
| If my company adopts 15 character pass-phrases as policy I don't want to 
| count on trusting the end users for the last character.
| If you've read this far I'll bet you have some comments and guidance. I'd 
| love to hear from you.
| 
| Thanks,
| Lawson...

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