Amazon on Tuesday filed a lawsuit against two companies that allegedly acted as “fake review brokers.”

The lawsuits filed in King County Superior Court in Seattle accuse the companies, AppSally and Rebatest, of fostering fake reviews on Amazon’s online marketplace. The companies allegedly connected third-party sellers with consumers who would leave a positive review of their product, in exchange for free products or payments.

The case represents Amazon’s latest effort to root out fake reviews on its sprawling third-party marketplace. The marketplace now accounts for more than half of Amazon’s e-commerce sales and has helped the company bring in record revenue. But fake reviews have proven to be a particularly thorny issue for Amazon as the marketplace has grown to include millions of third-party merchants.

By filing the complaints, Amazon said it’s aiming “to shut down two major fake review brokers,” that it claims “helped mislead shoppers by having their members try to post fake reviews in stores” like Amazon, eBay, Walmart and Etsy. AppSally and Rebatest say they have more than 900,000 users “willing to write fake reviews,” Amazon said.

Rebatest declined to comment. Representatives from AppSally didn’t respond to a request for comment.

AppSally and Rebatest have been in operation since 2018, according to court filings. The complaint alleges AppSally orchestrated a scheme wherein sellers would pay the company a fee, in some cases as little as $25, to receive “verified reviews.”

After providing AppSally with a link to their product, the sellers would ship out empty boxes and provide AppSally with photos to be included with a user’s review. Sellers would allegedly pay for the service with the hope that it boosted their product in Amazon search results. AppSally’s website allegedly promised sellers they’d be able to “outrank your competitors from your bedroom,” according to the complaint.

Similarly, Rebatest offered sellers a cache of reviews and other services to manipulate their product rankings, the suit alleges. Users would place an order for a product on Amazon and leave a review. Rebatest allegedly refunded a users’ purchase through services like PayPal.

Amazon seeks unspecified damages in both complaints, as well as an injunction from the companies that would bar them from selling or facilitating the sale of Amazon reviews.

Amazon is taking many steps to try and cut down on fake reviews and other fraud, including investments in machine learning tools and human moderators. It’s also asked other social media companies to step in and assist, as fake review communities have cropped up in Facebook groups and in messaging apps like Telegram, WhatsApp and WeChat.

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