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

From Windows 8 Security Technical Implementation Guide

Associated with IA controls: ECSC-1

SV-48422r1_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.

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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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