Network system and non-transitory computer-readable storage medium

A network system comprising:

• a service providing server configured to provide an application service;
• a user terminal connected to the service providing server over a network and configured to be used by a user when using the application service;
• and
• a proxy server configured to intervene between the service providing server and the user terminal, wherein
• the user terminal comprises:
• a terminal storage unit configured to store an application program that allows the user to use the application service, wherein the application program includes a whitelist for an application in which at least a URL of the proxy server is described;
• a service provision processing unit configured to access the service providing server over the network and execute a process of providing the application service to the user by starting the application program in response to an operational input by the user;
• a terminal comparison unit configured to, when an access request to a URL of an access target specified by the application program is made during the provision of the application service, compare the URL of the access target with at least one URL described in the whitelist for the application;
• and
• a terminal access control unit configured to, based on a comparison result, when it is determined that the access request to the URL of the access target specified by the application program is an access request to the URL of the proxy server, permit access to the proxy server, and configured to, when it is determined that the access request is an access request to a URL of an access target not described in the whitelist for the application, block access to the access target or permit access to the access target under a first predetermined condition, and configured to, when the application program is started, acquire version information of the whitelist for the application and transmit to the proxy server a request to confirm that the whitelist for the application is the latest list.