Even if a third party intercepts a packet flowing on the Internet, it is made difficult to identify which information processing apparatuses are performing communication with each other. In a communication system, there is provided a virtual address server for pooling a plurality of for-rent-out virtual global addresses to be temporarily used by a communication apparatus. When a first information processing apparatus performs communication with a second information processing apparatus, the first information processing apparatus requests the virtual address server to rent out a virtual global address. Next, based on this request, the virtual address server rents out this virtual global address. Moreover, the first information processing apparatus sends out a communication packet whose transmission-source address is set up by this virtual global address and whose transmission-destination address is set up by the global address of the second information processing apparatus.