[COLOR=royalblue]The most benign of these programs simply serve advertisements. Others can collect detailed information about a viewer's behavior and send it back to a parent company the person likely knows nothing about. Many change the settings of a browser or other software, sometimes in ways that only someone with sophisticated technical knowledge can reverse.
None of this is illegal, and in most cases, notice of such functions is contained somewhere in a piece of software's terms of service or license agreement. But critics say few people read these agreements. As a result, incautious surfers can often unknowingly wind up with software that monitors their behavior, soaks up their computing and network resources, and can even damage their computers, in extreme cases.[/COLOR]