When providing a user with native access to at least a portion of device hardware, the user can be prevented from modifying firmware and other configuration information by controlling the mechanisms used to update that information. In some embodiments, an asymmetric keying approach can be used to encrypt or sign the firmware. In other cases access can be controlled by enabling firmware updates only through a channel or port that is not exposed to the customer, or by mapping only those portions of the hardware that are to be accessible to the user. In other embodiments, the user can be prevented from modifying firmware by only provisioning the user on a machine after an initial mutability period wherein firmware can be modified, such that the user never has access to a device when firmware can be updated. Combinations and variations of the above also can be used.