The LanMan authentication level will be set to Send NTLMv2 response only\refuse LM & NTLM.

From Windows Server 2008 R2 Domain Controller Security Technical Implementation Guide

Part of LanMan Authentication Level

Associated with: CCI-000366

SV-32300r1_rule The LanMan authentication level will be set to Send NTLMv2 response only\refuse LM & NTLM.

Vulnerability discussion

The Kerberos v5 authentication protocol is the default for authentication of users who are logging on to domain accounts.The Windows NTLM protocol is retained in later Windows versions for compatibility with clients and servers that are running earlier versions. It is also used to authenticate logons to stand-alone computers that are running later versions.

Check content

Analyze the system using the Security Configuration and Analysis snap-in. Expand the Security Configuration and Analysis tree view. Navigate to Local Policies -> Security Options. If the value for “Network security: LAN Manager authentication level” is not set to “Send NTLMv2 response only\refuse LM & NTLM” (Level 5), then this is a finding. The policy referenced configures the following registry value: Registry Path: HKLM\System\CurrentControlSet\Control\Lsa\ Value Name: LmCompatibilityLevel Value Type: REG_DWORD Value: 5 Documentable Explanation: In a mixed Windows environment, if this setting needs to be loosened due to compatibility issues, then the reasons need to be documented with the IAO.

Fix text

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”.

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