laser printers write an invisible codes on every page they print

As a way to track down counterfeits, laser printers print invisible marking containing information about the printer on every page. Manufacturers hope that this might help catch counterfeiters by tracing back which printer was used. Although this might look difficult because there are hundreds of printer manufacturers, but the important part is the printer engine, which is manufactures by few companies such as Toshiba and Canon. Dutch police has been successful to track many counterfeiters using this feature, other authorities has recently started using it in their investigations.