1. A storage controller which is connected to a plurality of clients for sending a plurality of packets, and a storage device for storing block data configuring a file, and which converts a file access request which is configured from one or more packets of a plurality of packets from the respective clients, to a block access request and sends this block access request to the storage device, the storage controller comprising: a packet monitoring processor which, upon receiving a packet, updates the amount of information corresponding to both a source client and/or target client of the received packet and a packet priority level set in the received packet, in priority level management information comprising the respective amounts of information corresponding to the respective packet priority levels for each client, on the basis of the amount of information in the received packet; an access reception module which specifies the file importance level corresponding to an access-targeted file specified in a file access request configured by one or more packets of the plurality of received packets, and on the basis of the amount of information of the access-targeted file, updates the amount of information corresponding to both a source client and/or target client of the access-targeted file and the specified file importance level, in importance level management information comprising the respective amounts of information corresponding to the respective file importance levels for each client; and a client determination module which, for each client, computes an assessment value for assessing whether a target client is appropriate or inappropriate based on one or more amounts of information corresponding to the target client and one or more packet priority levels, and one or more amounts of information corresponding to one or more file importance levels respectively corresponding to the one or more packet priority levels and the target client, and which determines whether the target client is appropriate or inappropriate in accordance with whether or not the computed assessment value conforms to a prescribed condition.