This sentence sounds awkward. It's not right for a few different reasons.
1) The reader will assume that which is describing company, not concept. The reader will always assume a modifier describes the noun closest to it. This is an example of a misplaced modifier. There is a good page here: http://www.chompchomp.com/terms/misplacedmodifier.htm I would suggest reading the last section, "Know how to fix a misplaced modifier." It involves whether you use a comma or not to separate the phrase from its closest noun. But in the case above, there are three nouns, and the comma would only help you distinguish between two.
2) "The concept which is about ethics" (not ethic) is vague. Is it an ethical concept (that is, a "good idea"), or is it a concept about a specific, ethical idea?
3) Prevails around the people is an unusual phrase. It suggests that something that prevails is something that can physically move near people. Prevails around the world or prevails around the company sound a little better, because it's clearer that the noun is not a physical thing.
Might I suggest the following sentences instead:
The concept, which involves ethics, prevails in the minds of the
This ethical concept prevails company-wide.