At the Aachen Summerschool applied IT security Steven J. Murdoch came up with an automatic way to analyze if the thumbnal in a JPEG file is different from the real image. There was widely discussed incident featuring a topless thumbnail and we wanted to know how widespread this problem is. So we crawled the net for images and used Steven's tools to filter for interesting ones. The tool outputs the main image (left) besides the thumbnail (right).

90% of the rest are cropped images. Sometimes just boring stuff has ben cropped, but on other instances interesting details where removed:









Then there are photoshopped images where the Thumbnail reveals the base for the modification:






Then there are a lot of Images where the Background has been removed:




Probably this is the most scary image: There the face has been obscured but the thumbnail contained the original face:



And finally there seem to be images where there are no similarities between the main image and the thumbnail:



And with certain images the tool sees differences where no differences are visible to the human eye:

You can do some screening yourself at http://sauna.5711.org/~md/thumbnails/