Apple has issued a warning to developers about using services that artificially boost the position of apps on the App Store charts, using promotional services that post fake reviews or automated sales via methods such as bot farms.

Apple posted a message on its Developer website warning that publishers “should avoid using services that advertise or guarantee top placement in App Store charts.”

It added that even if developers are not personally engaged in manipulating App Store rankings or user reviews but are using services that do so their behalf, it “may result in the loss of your Apple Developer Program membership.”

Apple suggests developers find tips and resources for marketing apps in more appropriate ways from the App Store Resource Center.