What is "ball tampering" in cricket? How can we say ball is tampered? Any punishments for tampering? Can somebody list the name of players who were punished?
As per law 42 (Fair and unfair play) (emphasis mine):
So it is illegal to alter the condition of the ball by actions except permitted in (a). Like, rubbing the ball on the ground, scuffing with a fingernail or other sharp object etc. Such actions are call as Ball Tampering.
This is up to the level of the ball tempering and the match referee. Usually the opposite team is awarded 5 penalty runs, the player is banned for few matches, is fined the match fee.
There was a big controversy of a ball tampering in the match between England and Pakistan in August 2006. ruled that the Pakistani team had been involved in ball tampering. They awarded 5 runs penalty to England and the ball was replaced. However, Pakistani team denied it and refused to play after tea. After waiting for few time, the umpires awarded the match to England.
It is an action in which a fielder illegally alters the condition of the ball. It'll make the fast bowlers ease to swing the ball in the air. So, it is easy to bowl reverse swing with (early overs)new balls.
The umpires will find whether the ball is tampered. They shall make frequent and irregular inspections of the ball. If the umpires together agree that the deterioration in the condition of the ball is greater than is consistent with the use it has received then they will apply the Law 42.1 on this action as an unfair Play.
The punishments will be differ on the possibility of finding the player(s) responsible for that action.
You can refer the ICC Playing conditions for test matches for the punishments on finding and not finding the player(s) responsible for tampering.