Utilizing a protected server environment to protect data used to train a machine learning system

A computer-implemented method comprising: storing, using a server computer executing within a protected environment, a plurality of media items, each of the media items corresponding to one of a plurality of different status values; receiving, from a requesting computing device that is outside the protected environment, a request to send certain media items outside the protected environment to a client computing device; computing, using a plurality of machine learning systems executed by the server computer, each of the machine learning systems having been trained with one of the plurality of status values as an output, a plurality of likelihood values associated with a particular status value for the client computing device, each of the machine learning systems having been trained at least in part using attribute values associated with health data records as inputs, and an existence or a non-existence of a one of the plurality of different status values as outputs, the server computer storing first data comprising a plurality of attribute values for a plurality of the health data records and second data indicating, for each health data record of the plurality of health data records, whether the health data record has the status value, the server computer being configured to train the particular machine learning system in the protected environment only if the first data and the second data satisfy a first criterion and being configured to send the particular machine learning system to the requesting computing device only if the particular machine learning system satisfies a second criterion; identifying a particular status value, among the plurality of status values, having a highest likelihood value; selecting a specific set of media items at least partly based on the identified particular status value having the highest likelihood value, in a number indicated by the request to send certain media items outside the protected environment to the client computing device; and sending, from the server computer to the client computing device, the specific set of media items that have been selected.