Apple has announced it will introduce a new privacy control feature in the spring. This new feature, known as App Tracking Transparency will prevent iPhone apps from secretly shadowing users. A general date has not yet been disclosed, but the new feature will likely be a part of an update that is planned to arrive late March or early April.
Apple has delayed the introduction of the new update to give Facebook and other app creators more time to adjust to the new feature. This is because it will require iPhone users to give consent to being tracked, which many will (unsurprisingly) deny.