More information would help. Remember that those who want to help you via the internet must see what you are seeing with your eyes. Without knowing what you see, helping is difficult.
What exactly have you done to detect it?
Is it a built-in webcam or an external one?
What make/model computer and what make/model webcam is it?
This link from Ubuntu may help you get started:
https://help.ubuntu.com/community/Webcam