This disclosure provides a system and method for client authentication that allows a service provider to implement multiple authentication challenges to verify a user/client. The system includes an extractor, a comparer, and an attributer. The extractor receives an Internet protocol source address from a client and extracts a media access control address. The extractor also determines a source identifier of the client from the media access control address. The comparer compares the extracted media access control address with a client media access control address associated with the client, and signals execution of one or more client authentication challenges when the extracted media access control address fails to match the at least one client media access control address associated with the client. The attributer associates the source identifier with the client after successful execution of a client authentication challenge.