Adware is an advertising computer program that can be put there by other people on someone's computer, sometimes without their permission. It is controversial because sometimes businesses put the program there so they can see what people are doing or what web pages they are browsing. They then put an advertisement that is of the same subject as the web-page the person is looking at. This can be good if the person is trying to buy something, but many people do not want advertisements. Many people also do not want other people to find out what they are doing or what web pages they are looking at. An example is in the popular peer-to-peer file sharing program, Kazaa. When someone downloads it, it installs adware on their computer that then sends advertisements to the computer. Some people do not like this so they use an illegally changed version of this program called Kazaa Lite.
Removal tools have been developed to assist users in clearing out these unwanted programs. Like many programs that people use for security, the program must be changed often. Updating allows the removal tool to recognize new types of adware. This can be done by downloading files over the internet using the 'update' option in the program.