This identifying information (and your Social Security number, if you provide it) is sent to an independent identity assurance service. They search public and private data sources and return a quiz designed so that only the person with that name, date of birth, and address will be able to answer the questions. The questions asked and the answers you choose are between you and the independent identity assurance service – the Department of Homeland Security is never told any additional information about you. When your identity is verified, the Department of Homeland Security is notified only that you may proceed to the next step in the Self Check process.
Official Website of the Department of Homeland Security