Cricket is a bit different to baseball because polishing the ball is an accepted part of the game. By polishing one side of the ball and allowing the other-side

Cricket is a bit different to baseball because polishing the ball is an accepted part of the game. By polishing one side of the ball and allowing the other-side to naturally grow dull you alter the flight characteristics of the ball - it's how you can achieve movement through the air or 'swing'. The ball is rarely replaced - it is very much intended for the condition of the ball to deteriorate over the course of an innings various tactics revolve around when to make bowling changes as some bowlers specialize with the 'new' ball which is shiny and hard and others have a style designed to exploit the older ball which is softer and more dull. There are certain time milestones that elapse in the match where captain can elect to replace a old worn ball with a new shiny ball. The illegal part is ball tampering rubbing some foreign substance against the ball such as dirt or mud to weight it down or scuffing up the ball with something (A player on the Australian team was caught using a strip of sandpaper, which was a big scandal over here recently).