Google experts worked on OS hardening and the implementation of anti-exploitation mechanisms with a great attention to the user privacy.
The tech giant updated the File-Based Encryption implementing the support for external storage media, it also included the metadata encryption with hardware support.
Android 9 also implements a new BiometricPrompt API, to have the biometric authentication dialogs that apps can display look the same.
Android 9 also comes with new protections for the Application Sandbox.