At most places I've worked, I had to sign a code of conduct that would say that if I witnessed something inappropriate or criminal, or received information I shouldn't have access to, I am responsible to report it and if I don't I am subject to discipline, up to and including termination of my employment. Last company I was at had a similar incident where we were offered proprietary information of one of our main competitors through a consultant who had previously done work at the competitor. The consultant was immediately dismissed and we immediately ceased doing business with the consulting firm he worked at and dismissed about 10 other consultants they had working at our company. We also notified our competitor about what had happened. It's about covering your own ass and also basic ethical behavior.