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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-21952	3.152	SV-25275r2_rule		Medium

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

STIG	Date
Windows 7 Security Technical Implementation Guide	2017-02-21

Details

Check Text ( C-60811r2_chk )
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

Check Text ( C-60811r2_chk )

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 (F-65543r2_fix)
Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Network Security: Allow LocalSystem NULL session fallback" to "Disabled".