The LAN Manager authentication level must be set to send NTLMv2 response only and to refuse LM and NTLM.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-225054	WN16-SO-000380	SV-225054r857283_rule		High

Description
The Kerberos v5 authentication protocol is the default for authentication of users who are logging on to domain accounts. NTLM, which is less secure, is retained in later Windows versions for 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 standalone or nondomain-joined computers that are running later versions.

Description

The Kerberos v5 authentication protocol is the default for authentication of users who are logging on to domain accounts. NTLM, which is less secure, is retained in later Windows versions for 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 standalone or nondomain-joined computers that are running later versions.

STIG	Date
Microsoft Windows Server 2016 Security Technical Implementation Guide	2023-08-22

Details

Check Text ( C-26745r466064_chk )
If the following registry value does not exist or is not configured as specified, this is a finding. Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \SYSTEM\CurrentControlSet\Control\Lsa\ Value Name: LmCompatibilityLevel Value Type: REG_DWORD Value: 0x00000005 (5)

Fix Text (F-26733r466065_fix)
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".