A student offered me money to take one of his exams in his place. What should I do? Briefly, I am currently offering my services as a math tutor on a dedicated website.
Recently, a university student contacted me and offered me money to help him cheat an incoming exam. The arrangement would be easy since the exam will take place online, due to COVID-19 (the student would send me the exam text and I would send it back to him, once completed).
I have refused due to ethical reasons. Now, I have identified the precise university and course, and I am wondering if I should warn the course professor that at least one anonymous student has attempted such an arrangement.
I have thought some arguments pro and against:
Against:

such kind of cheating is obvious and warning the professor would
serve no purpose. I would just annoy the professor.
It could happen that the professor will ask me to identify the student. I don't know the student's name, but I have some information
about him that could identify him. Now, in this case, I would refuse
to attempt to identify the student because 1) no actual cheating has
happened yet and 2) it is a can of worms I don't want to open 3) I
don't want to see anybody reprehended, I just would like to prevent
the cheating from happening

Pro:

there are ways to prevent the cheating from happening (browser lock +
full webcam view of the student would make this kind of cheating
quite difficult). Thus the warning is not meaningless.
Even if the professor has already considered the possibility of such
an arrangement, it is still the right thing to do, and the professor
won't be annoyed in either case.
Realistically, the professor won't ask me to identify the student.

These are my thoughts about the matter. I am open to advise. Especially, I would like to know the opinion of actual university professors, if possible.
My advice would be to inform the professor that &quot;students&quot; have contacted you with improper requests such as ...
You were correct to refuse the student, but you may have an obligation to keep them anonymous, as you suggest. That would be true if you have a client relationship with them already, I think.
But the university needs to become aware, if they aren't already, that they need better procedures in place to assure academic integrity. At this time, many are trying (and failing) to get it right and your mail might be a goad to try harder.
You can refuse to help identify the student, but you can certainly make suggestions about improving security.
If your website or other contact methods don't already say it, you might put up a notice of some kind listing what you do when asked to help with cheating.