The navigation of ships relies to a considerable extent on the Electronic Chart Display and Information System. In this talk, an introduction to our research project is given. We identified manipulation possibilities of the ship's navigation systems. It has been shown, that it is possible to introduce unnoticed manipulated nautical charts and routes into the system or to manipulate input data like that from the GPS receiver. It will be shown, that this results in a risk to shipping in a narrow fairway such as the Elbe river. A collision or seagoing could be the result. The IT security on board should be given as much importance as other security measures of the ship and its crew.