Mark Wigfield with the FCC has responded, saying in an email:

"There are many different methods built into the NLAD (National Lifeline Accountability Database) to protect subscriber information. Subscriber information is protected by the use of secure internet protocols, encrypted data transfer requirements, and real-time monitoring of the database. Only authorized users have access to the NLAD. Authorized users in each company only have access to their own subscribers and cannot see information of other companies."