Device risk level based on device metadata comparison

An authentication system determines a risk level for a client device impersonating a client device enrolled in authentication services by comparing device metadata for the impersonating client device to device metadata for the enrolled client device. As part of enrolling the enrolled client device, the authentication system associates one or more authentication credentials with the enrolled client device. In order to authenticate access requests associated with a client device identified as the enrolled client device, the authentication system obtains an authentication token from the client device generated using the authentication credentials and also obtains device metadata corresponding to the client device. Based on the device metadata comparison during authentication, the authentication system detects device metadata anomalies and uses detected device metadata anomalies to determine a risk level for the client device. Based on the risk level, the authentication system authorizes or denies the client device from accessing requested services.