In a case where a master virtual machine, which is constructed on the basis of master information for configuring either part or all of a virtual machine, and an individual virtual machine, which is constructed on the basis of individual information that is configured partially or entirely in accordance with the master information, exist as the types of virtual machines that a physical client provides to a user terminal, a security check of a plurality of virtual machines is selectively executed, with respect to each check item, for a virtual machine of the type corresponding to the contents of the check item.