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

From Windows 7 Security Technical Implementation Guide

Associated with: CCI-000366

SV-25275r2_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

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: Allow LocalSystem NULL session fallback" is not set to "Disabled", this is a finding. The policy referenced configures the following registry value: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \SYSTEM\CurrentControlSet\Control\LSA\MSV1_0\ Value Name: allownullsessionfallback 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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