Patent ID: 8243606

Claim:
An information acquisition device comprising: an acquiring unit that acquires a first group of packets which are transmitted from an address converting and transmitting device receiving a second group of packets from a plurality of terminal devices, converting the source address of the packets of the second group from the address of each of the terminal devices to the address of the address converting and transmitting device, and transmitting, as the first group of packets, the second group of packets with the source address converted, each of the packets of the second group including an address of each of the terminal devices as a source address and an identifier generated by adding a numerical value every time a packet is sent by each of the terminal devices; an identifier storage unit that stores the identifier in association with the source address included in the first group of packets acquired by the acquiring unit; an identifier determining unit that determines whether the identifier for a certain source address stored has strongly increased; and an address converting and transmitting device detector that detects, as the address of the address converting and transmitting device, the certain source address for which the identifier determining unit determines the identifier has strongly increased.