Detection of content viewing

Patent Granted PROBLEM TO BE SOLVED: To enable detecting of viewing of a content in real time without applying any processing to the content itself. ; SOLUTION: A transmission traffic pattern observed when a digital content is transmitted from a server 1 and a part of a reception traffic pattern observed when the content is reproduced at a user terminal 2-i (i=1-4) are subjected to a matching process. When it is determined that they are correspondent, it is determined that the digital content transmitted from the server 1 is viewed at the user terminal 2-i.