This invention is to appropriately cope with abnormal states. A control method according to the present invention includes: identifying an abnormal level according to abnormal level reference data stored in advance in an abnormal level reference data storage, from context relating to abnormalities, which has been collected in advance and stored in a context storage; and converting the identified abnormal level to an authentication strength level according to a predetermined authentication strength level setting rule, and causing an authentication server to carry out an authentication processing according to the authentication strength level. By carrying out such a processing, it becomes possible to cause the authentication server to carry out an authentication having an authentication strength level corresponding to an abnormal state.