Silent Network Authentication (SNA) is a new authentication method that uses GSM authentication under the hood to verify users with their mobile carriers without requiring any user input, providing strong security assurance without added friction. To use SNA, developers need to sign up for a Twilio account, request access to the API and Live Test Number feature, add their personal phone number in the console, create a Verify Service, and follow the 3-step verification process that involves starting the verification process, invoking the sna.url from a mobile device, and checking the verification status. SNA uses network authentication and can be used for production usage with carrier approval required. Developers need to handle errors and implement best practices to ensure successful implementation of SNA in their applications.