Software pirates are distributing bootleg versions of Spotify, Angry Birds, Pokemon Go, and other popular apps available for iPhone, according to a new report by Reuters. Using digital certificates, illegitimate software distributers including TutuApp, Panda Help, AppValley and TweakBox have gained access to an Apple program that lets companies distribute business-related apps to employees without involving the heavily monitored App Store.

These software pirates are able to use the enterprise developer certificates to tamper with apps by removing ads, rules, and fees that a normal customer may experience. The hacked apps are then distributed to iPhone users, stripping Apple and trustworthy app developers of revenue. This is a clear violation of Apple’s developer program rules, which state all apps must be distributed through the App Store.

“Developers that abuse our enterprise certificates are in violation of the Apple Developer Enterprise Program Agreement and will have their certificates terminated, and if appropriate, they will be removed from our Developer Program completely,” an Apple spokesperson told Reuters. “We are continuously evaluating the cases of misuse and are prepared to take immediate action.”

According to Reuters, Apple is not able to track the fraudulent spread of certificates or hacked apps but can cancel a certificate if they find it has been misused. Unfortunately, software pirates can easily find a new certificate to use if their old one is compromised.

Since Apple can’t track the illicit activity, they also can’t estimate how much money they’ve actually lost. TutuApp distributes Minecraft for free, a game that normally costs $6.99 in the App Store. AppValley offers a hacked version of Spotify that removes all advertisements, a feature that Spotify Premium subscribers usually have to pay up to $10 a month for.

Software pirates can make a profit by offering a membership that costs $13 or more a month for access to “VIP” versions of the apps, which are said to be more secure than the free versions.

Apple has confirmed that the company plans to implement a two-factor authentication method, requiring all app developers to provide a code sent to a phone and a password. Apple plans to release the security update by the end of the month. App developers that have been affected by the pirating have begun releasing statements condemning the modification of their software, such as Spotify and Angry Birds creator Rovio.