1. A computer-implemented method comprising: accessing, by one or more computers, a first data set of live images of at least one person; accessing, by the one or more computers, a second data set of fabricated images of at least one person; obtaining, by the one or more computers, measurements of characteristics of images in the first and second data sets; storing, by the one or more computers and in a data store and for each image in the first and second data sets, (i) the measurements of characteristics of the image and (ii) an indicator of whether the image is from the first data set or from the second data set; determining, by the one or more computers and for the aggregate of images in the first and second data sets, a statistical relationship between the indicator of whether the image is from the first data set or from the second data set and the measurements of characteristics of the image; and selecting, by the one or more computers and based on the statistical relationship, one or more relevant characteristics from among the characteristics of the image that are determined to be relevant in identifying whether an image is a live image or a fabricated image.