This paper introduces an external storage middleware, that offer a set of functions (API - Application Program Interface) to mobile applications and facilitates the transfer of file between a mobile device and external storage servers
regardless of the available wireless network. The Middleware selects the best wireless service available. In addition,
the file exchanged between the mobile device and the external storage server are encrypted to provide security when
traveling through the network. As a use case, it was developed an automatic file swapper service for mobile devices.
The service is running on the mobile device optimizing its
available storage space. Our middleware was tested with the
following wireless services: Wi-Fi, GPRS, MMS.