Some of China’s biggest technology companies, including ByteDance and Tencent, are testing a tool to bypass Apple’s new privacy rules and continue tracking iPhone users without their consent to serve them targeted mobile advertisements.

Apple is expected in the coming weeks to roll out changes it announced last June to iPhones that it says will give users more privacy. Until now, apps have been able to rely on Apple’s IDFA system to see who clicks on ads and which apps are downloaded.

In the future, they will have to ask permission to gather tracking data, a change that is expected to deal a multibillion-dollar bombshell to the online advertising industry and has been fought by Facebook, since most users are expected to decline to be tracked.