What would you do if you were made aware of a co-worker being dishonest or stealing from the company?

"Unfortunately, dishonest employees are everywhere, and I certainly would not consider myself a 'whistle-blower' in the workplace. If I found that a co-worker was stealing or doing anything to harm the company, I would directly ask what was going on. There is a good chance of the situation being a simple misunderstanding. If it wasn't a misunderstanding and the co-worker was outright defiant with their damaging actions, then I would bring it, professionally, to the appropriate parties."