The U.S. Federal Trade Commission today finalized a ban on companies knowingly buying or selling fake online reviews, giving the agency the power to levy fines against the shadowy practice.

The ban covers trafficking in fake reviews, whether by non-existent customers, company insiders or artificial intelligence. It also prohibits buying and selling fabricated views or followers on social media, and using intimidation tactics to remove negative reviews.

The FTC can seek a maximum penalty of up to around $51,744 per violation.

“Fake reviews not only waste people’s time and money, but also pollute the marketplace and divert business away from honest competitors,” FTC Chair Lina Khan said in a statement.

The rule does not require platforms that simply publish consumer reviews to verify their veracity.

Teresa Murray, a consumer advocate at U.S. Public Interest Research Group, said the rule is an important protection for online shoppers, 90% of whom base purchase decisions in part on reviews.

“We hope this puts fear in companies so they do the right thing, even if it’s just because they’re afraid of the consequences,” Murray said.