To prevent leak of a content by preventing the unauthorized use of the content on a client side, in addition to prevention of an unauthorized access to a server storing and holding the content.

A server 3 includes a content processing part 3a and a filter processing part 3b. The client 1 accesses the filter processing part 3b and requests a file acquisition. The filter processing part 3b temporarily stores an original file obtained by requesting a file to the content processing part 3a, and transmits a container HTML containing not the original file but a script for starting an exclusive browsing program. The client 1 starts the exclusive browsing program by the script contained in the container HTML, receives the coded original file, and browsably decodes it.