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

From Windows 8/8.1 Security Technical Implementation Guide

Part of SPN Target Name Validation Level

Associated with IA controls: ECSC-1

Associated with: CCI-000366

SV-48416r2_rule The service principal name (SPN) target name validation level must be configured to Accept if provided by client.

Vulnerability discussion

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.

Check content

Analyze the system using the Security Configuration and Analysis snap-in. (See "Performing Analysis with the Security Configuration and Analysis Snap-in" in the STIG Overview document.) 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 Subkey: \System\CurrentControlSet\Services\LanmanServer\Parameters\ Value Name: SmbServerNameHardeningLevel Type: REG_DWORD Value: 1

Fix text

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".

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