To provide an information transfer system for confirming a client who requests data transfer in an information network such as Internet.

In an information transferring system constituted of a client 10, information network 50, and data server 20, when a client requests data, a data server transmits an ID generation program to the client, and the ID generation program is executed in the client, and ID information for specifying the client is generated, and transmitted to the data server, and the data server analyzes the received ID information of the client, and transmits data to the client when the client ID information fulfills a prescribed condition.