1. A storage system that manages an access from a terminal via a network to a storage apparatus, the storage system comprising: an access instruction portion that sends an access instruction to the storage apparatus in response to being accessed from the terminal; and an access management portion that, in response to receiving the access instruction, sends a confirmation notification including sender information related to a sender of the received access instruction to the access instruction portion, wherein the access instruction portion comprises: an access instruction distinction portion that determines, on the basis of the confirmation notification sent by the access management portion, whether or not the sender of the access instruction related to that confirmation notification is the access instruction portion; and an unauthorized access instruction detection portion that determines, on the basis of determination result made by the access instruction distinction portion, the access instruction received by the access management portion from a sender other than the access instruction portion as an unauthorized access instruction, wherein the access instruction distinction portion determines that the sender of the access instruction related to a confirmation notification is the access instruction portion when the sender information included in the confirmation notification sent from the access management portion coincides with an identification provided by the access instruction portion for its own access instruction.