Abstract: A server is provided with: a group management section that manages an account of a group for information sharing and a user belonging to the group; a group account generating section that generates, when there is no group account corresponding to a destination of a message received from a user terminal, a group account corresponding thereto; a user registration section that registers a transmitter of the message as a user belonging to a group corresponding to the destination of the message; and a sharing section that causes data transmitted from a terminal of the user belonging to the group to be shared by users belonging to a specified group.

Abstract: A server is provided with: a group management section that manages on a group-by-group basis a user belonging to a group for information sharing; a reception section that receives a message transmitted from a user terminal; a time limit setting section that sets a time limit to data sharing in the group based on destination information of the message; a sharing section that causes data transmitted from the user terminal of the user belonging to the group to be shared by users belonging to a specified group; and an invalidation section that invalidates the sharing by the sharing section in accordance with the time limit.