A system and method for the authorization of access to a service by a computational device or devices. A software agent generates a digital signature for the device each time it attempts to access the service and send it to an authentication server, which compares the digital signature sent with one or more digital signatures on file to determine whether access to the service is permitted. The digital signature is generated by using hashes based on software and hardware configuration data collected from the device. The system may be used in conjunction with other authorization methods and devices.