NTLM must be prevented from falling back to a Null session.

From Windows 10 Security Technical Implementation Guide

Associated with: CCI-000366

SV-78255r1_rule NTLM must be prevented from falling back to a Null session.

Vulnerability discussion

NTLM sessions that are allowed to fall back to Null (unauthenticated) sessions may gain unauthorized access.

Check content

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\MSV1_0\ Value Name: allownullsessionfallback Value Type: REG_DWORD Value: 0

Fix text

Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Network security: Allow LocalSystem NULL session fallback" to "Disabled".

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