An authentic scanner driver 11 provided with a function of preventing unauthorized use is installed in a personal computer 10. Data is sent and received with a color scanner 20 via the driver. The color scanner 20 is provided with a driver recognition portion 22 for making a decision as to whether the connection target is an authentic driver. Only where the driver is judged to be an authentic driver, normal image processing (acceptance and transfer of data) is performed. Where the driver is not an authentic driver, the normal image processing is stopped. Thus, the unauthorized use preventing function incorporated in the driver is operated with certainty. Monitoring is done to detect whether fraudulent processing such as forgery is performed. Consequently, unauthorized use can be prevented.