Students write papers in many of their courses to improve their writing skills and to foster an active attitude toward learning. Every year, they hand in hundreds of papers for teachers to assess. This stream may get polluted in two ways: by simple copying from Internet sources and by the exchange of text fragments between students. These practices pose a serious threat to any kind of valid grading of individual performances. Fortunately, the very same Internet also offers us the instrument to clean up this stream. In this article, the authors discuss how they adopted "Ephorus" to help detect plagiarism. Although "Ephorus" is keeping students on the right track, there is still much to do during classes. In their teaching, the authors believe that prevention is better than punishment and that they should approach rookies and senior students differently. Their approach is a straightforward one: combine the inherent threat of detection through the use of a detection tool with clear instructions and carefully designed writing tasks. In their experience, the best one can do is to frustrate misconduct. Stimulate and reward the large majority that abide by the rules, and reserve punishment for the reluctant few.