Privacy Screen is a new feature introduced to Google Drive that , once activated, protects you Google Drive app on iOS devices via Touch ID. Although it is only limited to the mobile version of Google Drive but it is still a very important security measure to protect your files and folders from intruders. That being said, Privacy Screen does not provide full protection and the following items, according to Google may not be protected: “notifications, certain Siri functionality, files shared with the Files app, photos shared with the Photos app, and other system functionality”.
To enable Privacy Screen, open Google Drive app on your iPhone or iPad and click on settings and Select ‘Privacy Screen’
When you enable Privacy Screen you can then select whether you want it to be activated immediately after you switch to another app or select a delay time.
Courtesy of The Verge