It's possible that governments have been spying on our smartphone usage through our iOS and Android push notifications, according to an investigation conducted by U.S. Senator Ron Wyden and reported to the Department of Justice (via Reuters).
Senator Wyden warned in his letter that both Apple and Google can be compelled to release push notification data, Wyden's letter explains, which can contain metadata that is of interest to governments. This can detail the app, the device and the account of the person who received the notification, but could also contain other unencrypted content, including app backend functions or the actual text that has been sent to the user.
