Astroturfer

Companies now use "persona management software", which multiplies the efforts of each astroturfer, creating the impression that there's major support for what a corporation or government is trying to do.

Source: wiktionary

These Internet “astroturfers,” as they've been called, are supplemented by the hundreds of thousands of people who, in return for subsidized trips, gift cards, free samples, and modest payments, have signed up to be word-of-mouth marketers under their own names, shilling wares to the people in their personal networks or writing positive reviews of products and services.

Source: wiktionary