s/CS//

In my university experience, the first day of every class starts with administrivia, which includes the grading policy, homework policy, and what degree of cooperation actually constitutes cheating. In CS, the usual threshold for cheating is whether or not you actually wrote the code yourself--you can (and are encouraged to!) work with other people to discuss how to solve the problem, but you have to sit down and actually write the code up yourself.

That said, as a TA, I found that I really didn't want to put any effort to identify if students were cheating. I did catch a few cheaters, but largely because they inadvertently broke my grading setup in ways that made me suspicious that they were getting their code from something other than the homework assignment.

In our course (first year intro CS), we run a tool called moss against thousands of submissions (it's a big class). Inevitably, we catch a few dozen cheaters on every assignment. Some of them are so brazen as to submit their friend's assignment as though it were their own, without even changing the name at the top of the file!

I also found a few likely cheaters in my stint as a TA. they sat together in labs and turned in nearly identical code for every assignment (down to some truly bizarre formatting choices). I didn't have the heart to turn them in since they were failing most of the assignments anyway.

Some cheaters make it impossible not to catch them. We had a guy using his phone during a math class. The professor came by and the kid had covered up his phone with a piece of paper. The phone is obviously not flat and the screen was up and still active, shining right through.