Running an IT service business for 7 years, I've run into a number of dubious situations. Heres a couple.
A client introduced me to a salesperson who works for a competitor company. We sat down for coffee, and his opening line was that he has a million dollars of deals in the pipeline (which would have been a very welcome addition to the bottom line), and he was interested in bringing all these customers to my business. Immediately after this, he asked for a very large base salary, which was a bit surprising given the time passed in the interview, but I suppose within general norms.
In any case, I was interested in bringing him on board, but since we're a smaller company, I'm very careful with my hiring decisions. As you all know, a wrong hiring decision can cause all sorts of problems and headaches for a small focused team.
So I started by asking him some more questions about his background, and some typical interview questions. Then he says :
"Actually, I know a good way we can start our relationship. There's a guy at work I really hate - a total prick. What if I were to give you all of his leads before he closes them? I can't give you an introduction or anything of course, but I can give you the client information, and the decision makers names, and you would have to sell them yourself! What do you think?"
I was taken back, and I responded : "Well, I'd need to examine the ethics and legality of that arrangement."
He responded : "Hey - we're all ethical here. This is just a way for us to start collaborating."
I ended the interview, already decided that I wouldn't hire him. If he was offering me this deal after knowing me for 20 minutes, how could I trust him as my salesperson once I hired him?
After this interview, I called a mentor to get his take. His immediate response was "Here's what you do. You call the CEO of the company he works for. Say 'I know we're competitors, but some information directly relevant to your company has come my way.' Meet up with him, and tell him exactly what happened. He'll be fired on the spot."
I didn't end up doing that. The salesperson was not the most moral of people, but he had a family to support, and it's very difficult to find a job in this down-market.
Another unrelated story - a customer manager who was a friend came to me and asked me for a kickback from the project he awarded me. Thinking back, he might not have realised how difficult a situation he put me in. Providing him with any kind of monetary payment would have been a touchy situation for many reasons, so I sat down with him and said something along the lines of :
"Actually, we're already running right against our profit margins for this project. Since you're a friend, I gave you a much bigger discount than I normally would give. I'd end up losing money here if I gave you a finders fee for this particular project. The fee I'd be able to pay probably wouldn't be worth your risk in accepting that kind of fee, or my risk in paying it. But, if you come across any other opportunities in different companies, I regularly provide finders fees for those situations so I'm happy to organise that for you."
By framing any kind of payment as risky, and by telling him we're not making much from this project because of our friendship, he dropped the issue, and everything turned out alright.
In summary - I tend to deal with corruption by avoiding it or deflecting it wherever possible. I don't tend to take the aggressive route of reporting it, or going after people.