It’s 3 a.m. Do you know what your iPhone is doing?

Mine has been alarmingly busy. Even though the screen is off and I’m snoring, apps are beaming out lots of information about me to companies I’ve never heard of. Your iPhone probably is doing the same — and Apple could be doing more to stop it.

On a recent Monday night, a dozen marketing companies, research firms and other personal data guzzlers got reports from my iPhone. At 11:43 p.m., a company called Amplitude learned my phone number, email and exact location. At 3:58 a.m., another called Appboy got a digital fingerprint of my phone. At 6:25 a.m., a tracker called Demdex received a way to identify my phone and sent back a list of other trackers to pair up with.

And all night long, there was some startling behavior by a household name: Yelp. It was receiving a message that included my IP address -— once every five minutes.

Our data has a secret life in many of the devices we use every day, from talking Alexa speakers to smart TVs. But we’ve got a giant blind spot when it comes to the data companies probing our phones.

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.

“This is your data. Why should it even leave your phone? Why should it be collected by someone when you don’t know what they’re going to do with it?” says Patrick Jackson, a former National Security Agency researcher who is chief technology officer for Disconnect. He hooked my iPhone into special software so we could examine the traffic. “I know the value of data, and I don’t want mine in any hands where it doesn’t need to be,” he told me.

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