A shill is a person who publicly supports or promotes a person, product, or organization while secretly having a close relationship or being paid by them. The shill pretends to be an independent and enthusiastic customer or supporter but is actually working to influence others in favor of the party they secretly support. This practice is common in media, marketing, auctions, and confidence games, and is often illegal because it can deceive others and cause harm. Shills can also act to discredit opponents of their client. The term originates from carnival slang and has been historically associated with someone who acts as a plant or stooge to manipulate crowd behavior.