Some thoughts: * Instead of hiding a "signature" in the files that coudl be removed, you could alter some poser setting by .0001 or so. If youw ork on a small decimal level over 5 settings or so you will gain 5 digits of information... enough for your purposes - and it will be difficult for peopel to just "rip out" an extraneous line. * It's VERY easy to hide data in JPG files - and there are already command line tools to do it. Do a search for "stenograpy" ... or you can do it in Photoshop with "digimark" - I think they have a free version? * Nerds method works well too... and might make a good adjunct to what you are thinking. * Taking LEGAL actionw ould be a real expensive proposition... but at least you could send them a scary email :) * The merchants blacklist of people suspected of warezing sounds like a good idea - but like all blacklists the danger is someone falsly accusing someone else as a form of attack or retribution.