A method of classifying an image taken by an image capture device, the method comprising the steps of: extracting an initial Sensor Noise Pattern (SNP) for the image; enhancing the initial SNP to create an enhanced SNP by applying a correcting model, wherein the correcting model scales the initial SNP by a factor inversely proportional to the signal intensity of the initial SNP; determining a similarity measure between the enhanced SNP for said image with one or more previously calculated enhanced SNPs for one or more different images; and classifying the image in a group of one or more images with similar or identical SNPs based on the determined similarity measure.