astroturfing
From Longman Dictionary of Contemporary Englishastroturfingas‧tro‧turf‧ing /ˈæstrəʊˌtɜːfɪŋ $ -troʊˌtɜːr-/ noun [uncountable] the practice of making people believe that a lot of ordinary members of the public like a product or support something and are not being paid to say this, when really it is part of an advertising or political campaign —astroturfer noun [countable]