Hacked versions of iPhone apps like Spotify, Minecraft and Pokemon Go were sold by software pirates who hijacked Apple technology.
Reuters reports that Enterprise Developer Certificates are being used to allow users to stream music without advertising and bypass game fees and rules – meaning that Apple and legitimate app makers are losing money.
The pirate developers violate rules whose status apps can only be distributed to the public via the App Store.
The pirates allegedly producing the apps – such as TutuApp, Panda Helper, AppValley and TweakBox – did not respond to requests, Reuters comments.
Apple has no way to track the distribution of modified apps, but can cancel the certificates if they are misused.
"Developers who abuse our corporate certificates are in violation of the Apple Developer Enterprise Agreement, and their certificates are terminated, and they may be completely removed from our developer program," Apple spokesman told the news agency.
"We are constantly investigating the cases of abuse and are ready to take action immediately."
Enterprise Developer Certificates are designed to give organizations the ability to distribute apps to their employees without performing App Store reviews.
Some of the pirate developers were banned by Apple last week, but were reportedly restored within days with various certificates.
"There is nothing that prevents these companies from doing this again from another team, another developer account," said Amine Hambaba, security manager of the software company Shape Security.
Apple has now said it's getting tougher with rogue apps if two-factor authentication – using a code sent to the phone and a password – is used to sign in to all developer accounts by the end of the month.
Spotify declined to comment on modified apps, but said earlier that its new terms of service will be applied to users who "create or distribute tools that block advertising".
Pokemon Go maker Niantic said gamblers cheating on fake apps are banned on a regular basis. Microsoft, which owns the hit game Minecraft, also declined to comment.