Retail giant Amazon is suing more than a thousand people it believes have been posting fake product reviews on its website.
The company says 1,114 defendants, nicknamed "John Does" as the company does not yet know their real names, have offered a false review service for as little as $5 (£3.24) on the website Fiverr.com.
Many of these promised the maximum five-star reviews for a seller's products on the site, it is claimed.
Anyone can sell products on Amazon's Marketplace site - a challenger to the auction bid giant eBay.
However, sellers can receive reviews from those visiting their product pages and an amalgamation of star ratings appears beside their profiles on the site.
The incentive to seek to pay for the best possible reviews would be to portray a high-quality service and good customer satisfaction.
But now Amazon believes many of these reviews may be illegitimate.
Its investigation found over a thousand people involved in the practice of posting reviews in exchange for cash.
People were using multiple accounts from IP addresses, it found.
"While small in number, these reviews can significantly undermine the trust that consumers and the vast majority of sellers and manufacturers place in Amazon, which in turn tarnishes Amazon's brand," the company said in its complaint, which was filed in Seattle on Friday.
Fiverr, which allows people to sell their services for payments, says it is working with Amazon to solve the problem.
Customers and non-customers can post reviews on products and on seller's own profile pages but the company expressly forbids the posting of reviews in exchange for money.
It tags genuine customer reviews with a 'Verified purchase' moniker to increase authenticity.