Disable Microsoft Windows LM / NTLMv1 Authentication

How can I disable Microsoft Windows LM / NTLMv1 Authentication  on all the computers in my domain?

I'm hoping this is a group policy.
Thomas TurnerAsked:
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JohnBusiness Consultant (Owner)Commented:
Here is the Microsoft Knowledgebase article for NTLM 2 authentication.


I set my LSA registry key value to allow access between my old virtual machines and my Windows 8 machine.

Why do you wish to disable it?  I cannot think of any need and I am not sure it is a good idea.
Mohammed KhawajaManager - Infrastructure:  Information TechnologyCommented:
You could disable NTLMV1 by by changed the value to 5 for:
HKLM\SYSTEM\CurrentControlSet\Control\Lsa\lmcompatibilitylevel to 5.

You could also create a GPO to disable LM as per link below:


Even with all of this, password hashes are stored in LM hash in memory if password is 14 characters or less.  Refer to this link below for more information:


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Mohammed KhawajaManager - Infrastructure:  Information TechnologyCommented:
Also note that you cannot disable LM or NTLM1 if there computers older than XP for workstations and NT for servers.
Thomas TurnerAuthor Commented:
Thanks for the heads up
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