Most common ways of cheating on exams?
The most common issue I observed is looking at other students' exams. A student who has a particularly good eyesight sits behind a second 1-alpha student and copies from the sheets of the latter student.

You forgot several variations on the topics you've mentioned, such as hacking to


obtain the exam in advance
modifying the exam in advance
modifying the student's answers a posteriori.


We see attempts of such actions, and we have no idea of how many such attempts have been successful. It can be anything between 0% and 99%.
Another common thing we see are attempts to bribe the teaching assistants. It does happen, although rarely.