Methods and devices are provided for detecting or preventing unauthorized upgrades to a customer's quality of service in an access data network. Several aspects of the invention require customer nodes to properly perform an initialization procedure. For example, the initialization procedure may involve making a request to a server controlled by, or at least trusted by, the service provider. The initialization procedure may involve downloading a configuration file, such as a DOCSIS configuration file, from the trusted server. According to some such aspects of the invention, nodes that cannot properly perform the initialization procedure are prevented from coming online. According to other such aspects of the invention, nodes that cannot properly perform the initialization procedure are marked. A warning may be sent to marked nodes. A customer associated with a marked node may be charged a higher rate for service.