a second storage conventionally authenticates a host computer , but this is weak in a disguise attack . further , since there is provided only an option of two ways : connection authorization and connection rejection , an intrusion into the host computer directly leads to destruction of data in the second storage . therefore , a plurality of network transportation ports are provided and connected to different networks , respectively , and an access right to data in a second storage is specified for the transportation port . furthermore , it can be specified whether or not the access for each i / o command is authorized .