Security Basics mailing list archives

Re: Password Management


From: Derek Schaible <dschaible () cssiinc com>
Date: Tue, 25 Apr 2006 08:03:33 -0400

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On Apr 21, 2006, at 4:44 PM, Utz, Ralph wrote:

The reasoning behind 7 being the magic number is because of how the
passwords are stored on the DC. Say you have a 9 character password.
When it is stored, it is broken down into hashes. Each hash is 7
characters long. So when that password gets stored, it is broken into
two hashes, one that is 7 characters full, one that only has 2
characters. The hashes are not padded, so the last hash is weak due to
only having two characters in it.

You are describing the very old LAN Manager Hash or LM Hash which was used in the early days of NT and Win95/98 clients. Modern Windows Domains use NTLM, NTLMv2 and/or Kerberos (the default if you have a modern Win2K3 domain filled with XP clients) . While each of these has their own potential for exploitation (no authentication system is infallible), they do not use the LM Hash and Microsoft recommends disabling the LM Hash from your domains entirely via GPO's. It is still supported by default to support legacy clients but without those clients on your network, it won't be used unless something is seriously wrong with your authentication scheme.

All that said, usually the longer the password, the better. I say usually because BermudaShoreLine will probably be cracked long before "15()Lpjs][" would. It's not just length that matters, its content and complexity as well.

HTH!

- -d


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