An apparatus includes a processor that monitors transmissions destined for an external network, determines that a transmission includes original media associated with a subject, and intercepts the transmission before it reaches the external network. The processor generates modified media by selecting a subset of data elements of the original media and replacing a value of each data element of the subset with a new value. At least one of the subset of data elements and the set of new values is chosen such that an accuracy metric calculated for a first generative algorithm, trained to generate synthetic representations of the subject based on modified media, is less than, by a given factor, the accuracy metric calculated for a second generative algorithm, trained to generate synthetic representations of the subject based on original media. The processor replaces the transmission with a new transmission that includes the modified media.