Software with this behaviour is also called "scumware" by some. When you visit most mainstream sites, you will find advertisements for some products. Whenever a purchase is made via one of these ads, the webmaster of the first site (aka "affiliate") will receive a commision on the transaction. This logging happens either via URL parameters or cookies. Some programs however, detect this system in place and will overwrite the affiliates tracking with their own, hence "stealing" money from the webmasters.
