In order to back up a user's set of data (Ens) through a telecommunications network (RT), a terminal (TC) retrieves, from an application server (SA), a table (Tab) containing sets of risk factors (Frn) respectively associated with backup servers (SVn), assigns a trust level (Kn) to each backup server (SVn) identified in the table (Tab) based on the set of risk factors (Frn) associated with the backup server (SVn), selects at least three backup servers based on the trust levels (Kn) respectively assigned to the backup servers (SVn), and transmits the set of data (Ens) to each selected backup server (SVn), which saves the set of data.