The service principal name (SPN) target name validation level must be configured to Accept if provided by client.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-21950	3.150	SV-25273r2_rule		Medium

Description
If a service principle name (SPN) is provided by the client, it is validated against the server's list of SPNs, aiding in the prevention of spoofing.

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

Details

Check Text ( C-60807r2_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 "Microsoft network server: Server SPN target name validation level" is not set to "Accept if provided by client", this is a finding. The policy referenced configures the following registry value: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\ Value Name: SmbServerNameHardeningLevel Type: REG_DWORD Value: 1

Check Text ( C-60807r2_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 "Microsoft network server: Server SPN target name validation level" is not set to "Accept if provided by client", this is a finding.

The policy referenced configures the following registry value:

Registry Hive: HKEY_LOCAL_MACHINE
Registry Path: \SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\

Value Name: SmbServerNameHardeningLevel

Type: REG_DWORD
Value: 1

Fix Text (F-65539r2_fix)
Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Microsoft network server: Server SPN target name validation level" to "Accept if provided by client".