Abstract: A computer-implemented method for training an artificial intelligence based neural network is provided. At least one digital image of at least one security document is provided as a reference. A set of digital training images is provided, wherein these are altered compared to the digital image of the security document. The set of digital training images includes a first subset of positive digital training images having a visual impact of an alteration such that an unbiased human observer would consider a reproduction of the respective digital training image to represent the security document or multiple security documents. The set of digital training images includes a second subset of negative digital training images. Ground truth is provided to the neural network as to whether a reproduction of the respective digital training image is to be considered representing the security document or multiple security documents or not.