I taught a course before where students came to me and reported a few students cheating on an exam. I took it to the director and the dean and they both said that the information was hearsay. Basically they told me that if I didn't personally witness it, I could not enforce anything. I also couldn't punish the whole class by making them all retake the exam. In the end the director spoke with all of them as a class and they had to develop an honor code. Exams are now administered differently. I was curious to hear how other instructors have dealt with reported cheating in their experiences.