It is my first time posting in this forum. I have to first discuss the background of the title. Since this pandemic, our campus had switched to online format instruction(online classes and exams) for almost a year. For the exams throughout the year, some of my students decided to go against the honor code and post some questions from the copy of the exam that I made onto some forums or tutoring sites to cheat. At first, I was able to catch the cheating by searching the exam questions online with quotations and be able to find the exact match of the questions, which meant some of them cheated and I was able to warn them.
However, another semester passed and in the syllabus, I wrote on it that I am able to discover cheating using the above method(quotation) to hopefully discourage them from cheating. But now their method changed and I was told by my assistant that they decided to reword the sentences and change out all the variables of the questions(I am a statistic instructor) so the quotation method wouldn't work at all. How could I discourage my students from cheating and how can I discover the questions that the cheaters had posted online?