Washington Post – Apple says, “What happens on your iPhone stays on your iPhone.” Our privacy experiment showed 5,400 hidden app trackers guzzled our data — in a single week.

“…You might assume you can count on Apple to sweat all the privacy details. After all, it touted in a recent ad, “What happens on your iPhone stays on your iPhone.” My investigation suggests otherwise. IPhone apps I discovered tracking me by passing information to third parties — just while I was asleep — include Microsoft OneDrive, Intuit’s Mint, Nike, Spotify, The Washington Post and IBM’s the Weather Channel. One app, the crime-alert service Citizen, shared personally identifiable information in violation of its published privacy policy.

And your iPhone doesn’t only feed data trackers while you sleep. In a single week, I encountered over 5,400 trackers, mostly in apps, not including the incessant Yelp traffic. According to privacy firm Disconnect, which helped test my iPhone, those unwanted trackers would have spewed out 1.5 gigabytes of data over the span of a month. That’s half of an entire basic wireless service plan from AT&T…”