The present invention provides a system which maintains a function of monitoring and controlling a network regardless of an increase of data to be downloaded by a computer whose access to the network is restricted. The system includes: a first interface for transmitting and receiving data to and from the network; a second interface for transmitting and receiving data to and from the network; a determination component for determining whether or not network data received by the first interface is from a first terminal device; a first creation component for creating, in response to a determination made by the determination component that the network data is transmitted from the first terminal device, information causing a transmission destination address of the network data to be changed to an address of the second interface in a table of the first terminal device; a first transmission component for transmitting the information causing the transmission destination address to be changed to the address of the second interface; and a restriction component for restricting a bandwidth of the network data passing through the second interface to a predetermined value.