How far would you go to beat your competition?

Some Amazon sellers are using questionable tactics--flagging legitimate products as counterfeits and flooding product pages with fake reviews--to hurt rivals' listings and wipe out their competitors, The Wall Street Journal reports. Some have even bribed Amazon employees in the U.S. and India to gain access to internal company data, though these workers have since been fired, according to the report. While the Seattle-based e-commerce titan uses artificial intelligence to stop bad actors before they strike, there are still a few schemes that get past the machines.

Here are four ways Amazon scammers are undercutting the competition, as reported by WSJ.

1. Tainting products with phony infringements

Merchants are flagging legitimate products as counterfeit or as infringing trademarks. When Amazon removes the listings from its platform while the items are under review, customers can no longer find or buy your products.

2. Selling wholesaler accounts on the black market

Scammers are turning to the black market to acquire Amazon wholesaler accounts for as much as $15,000 or renting them for about $1,500 per month. Because these accounts are supposed to be used by wholesalers, they have access to product listings and the permissions to modify them. Some rivals use them to hurt competitors' listings by altering their product pages, including switching photos with an unrelated item.

3. Writing fake product reviews

Some sellers are flooding rivals' product pages with fake reviews, either overly positive or negative. In other cases, sellers engage in a tactic known as "brushing," in which fake accounts use real addresses to order an item and post a review. Amazon actively monitors fake review activity, so it may remove even some of your legitimate reviews if it believes the product page contains suspicious comments.

4. Tricking Amazon's algorithm

Some sellers repeatedly click on links to products they want boosted, so they appear higher on Amazon's search results.