A computing system may determine different patterns of modifications that are to be made to data of a file to generate respective modified versions of the file, the different patterns of modifications enabling identification of other files derived from the respective modified versions of the file, the different patterns of modifications including a first pattern of modifications. The computing system may generate a first modified version of the file at least in part by modifying the data based on the first pattern of modifications, may send the first modified version of the file to a client device, and may store signature data indicative the first pattern of modifications so as to enable identification of other files derived from the first modified version of the file.