Crippleware is a classification given to some "free" software which is highly limited in functionality. The most common crippleware are virus scanners or system optimization programs. In general, crippleware will evaluate a person's system somehow (or pretend to), then tell them about all the "problems" (real or fake) which it needs to fix. When the person tells the software to fix the issues, it will inform them that they must buy the program to continue. In all, these are nothing more than advertising gimmicks. For this reason, such software also falls under the umbrella category of Potentially unwanted programs.