[psyklic]

That does not implicitly declare that a test bank is okay to study from, since it says on it that it is not for students. Any student would question to themselves whether they should use it. So ethically speaking:

1) Ask the professor before the exam if it is okay to use the test bank. He will say, of course not! Why do you have it anyway, it's not made available to students - are you trying to cheat?!

2) Astonished that the test bank was the exam verbatim (though I'm sure few students were), students should have told the professor that many students used the test bank, not realizing he would pull the questions directly from it. Of course, no one would do this directly since students aren't supposed to have the test bank in the first place ...

[ndl]

1) Many of the students probably received the test from their peers and did not know that it had come from a private test bank. I seriously doubt 200 people independently and individually broke into the same test bank, unless it was actually open to students, in which case it was as much fair game as the rest of the Internet. There are plenty of universities that keep student-accessible test banks and records of old exams (including the two I've attended), so many students probably assumed it was from that type of source.

1.5) Also note that the concept of a "test bank" that is supposedly inaccessible to students is not entirely common knowledge. We don't know how easily accessible and/or clearly warned this information was.

2) I already said that the students were wrong not to mention that they'd seen the test.