A data distribution system, method and program for generating a distribution package for distribution data to a client. An environment of a requesting client requesting distribution data is detected. A determination is made of an access control execution program for implementing an access control mechanism and a loading unit on the requesting client. The access control execution program is adapted to the detected environment of the requesting client and control access to a resource from a process in the client. The loading unit loads the distribution data to a protected storage area of the client. A determination is made of a security policy specified for the distribution data. A distribution package is generated including the distribution data, the security policy, the loading unit, and the access control execution program adapted to the environment of the requesting client; and transmitting the generated distribution package to the requesting client.