Network Access: LAN Manager authentication level must be configured to send NTLMv2 response only and refuse LM and NTLM.

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The Kerberos v5 authentication protocol is the default protocol for authentication of users who are logging on to a Windows domain with domain accounts.

NTLM, which is less secure, is retained in later Windows versions for backwards compatibility with clients and servers that are running earlier versions of Windows, or applications that still use it. It is also used to authenticate logons to stand-alone computers that are running later versions.

Remediation

GPO: Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Network security: LAN Manager authentication level" to "Send NTLMv2 response only. Refuse LM & NTLM".

Stig Windows Server 2016: https://www.stigviewer.com/stig/windows_server_2016/2020-06-16/finding/V-73691
Stig Windows Server 2019: https://www.stigviewer.com/stig/windows_server_2019/2020-06-15/finding/V-93301
Stig Windows Desktop: https://www.stigviewer.com/stig/windows_10/2021-03-10/finding/V-220938



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