Abstract: A security enhancement apparatus is provided which is capable of preventing infection by malware that requires writing of important files of the OS or system, by protecting the important files from writing if data protection is implemented in units of files. The security enhancement apparatus relays IO of a PC, control device, or the like. A hard disk, USB device, display, or the like is connected via the security enhance apparatus. As for data protection in a storage, data is handled not only in units of sectors but also in units of files. The apparatus directly performs secure data transfer or display, setting/input therefor, or the like, thereby being able to correctly make an alert or inquiry to the user even in the case where a vulnerability of the OS or application program is attacked and control of the PC or control device is taken by an unauthorized program. Also, during communication, the security enhancement apparatus can authenticate a communication-partner device and encrypt communication content.