digital – Horizontal “Lines” affecting image quality

This is a picture from my computer camera (0.9 MP) of me covering the camera with a black tissue with not much light in the room. I hope you can appreciate the tiny horizontal “lines”. I took a photo while covering the camera in order they are easily seen, but they appear all the time. Also, they aren’t static.

I would like to know what phenomenon cause them, if it’s posible to solve it and how. Thanks.