Apple's new App Store privacy guidelines restricting apps that collect data on users' friends - specifically, the address books of iPhone users - already seemed to be in large part a response to Facebook's sprawling Cambridge Analytica data scandal.

But the company could also be targeting Facebook's Onavo Protect VPN service, which poses as a way to grant users anonymity from service providers and websites but is explicitly designed to vacuum up huge amounts of data on the device usage habits of anyone who enables it.