Thanks for writing to us.
You can definitely secure your App by applying ACL either on User Data or Method Level Calls. On a Method Level, you can create a separate key for your App and give access to required methods for that key. ACL app are more secure in the way that one app user cannot access data of another user until user gives permission to access it.
Kindly follow the link which helps and provide a detailed information for securing your app information.
Let me know if it helps.