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

From Windows 8 Security Technical Implementation Guide

Part of SPN Target Name Validation Level

Associated with IA controls: ECSC-1

SV-48416r1_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.

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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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