The devices are known as 'fully loaded' Kodi boxes. They allow purchasers easy access to illegally available content online, such as live sports matches and film streams.
But now Facebook is clamping down. It's updated its commerce policy to ban the sale of "products or items that facilitate or encourage unauthorised access to digital media."
Promote the sale of these devices on Facebook, and you could find yourself banned from the social network.
The Federation Against Copyright Theft (FACT) welcomed the move.
"It is great to see Facebook follow the likes of Amazon and eBay in making changes to their policies to prohibit the sale of illicit streaming devices on their platforms," said Kieron Sharp, FACT's director general.
"These days social media sites are more than just a place to share photos and comments with friends and family. Unfortunately, the fast-paced development of these sites are being exploited by opportunists for criminal activity which needs to be disrupted."
Kodi boxes aren't illegal in themselves, it's the promotion of so-called 'fully loaded' models that attracts the long arm of the law. Our advice? Steer well clear.