'A number of popular iOS apps are collecting personal data without users' knowledge.
After hooking an iPhone up to monitoring software, The Washington Post discovered that more than 5,400 app trackers were sending data from the device to third parties.
The scope of data collected are wide ranging, with trackers sweeping up sensitive information like emails, phone numbers, IP addresses and a user's exact location, among other things.
App trackers are often busiest at night, when the device owner is asleep, or at times when a smartphone isn't being used.
They often take advantage of Apple's 'Background App Refresh' feature, which allows apps to transmit data when they're not actively being used, primarily for the purpose of making sure they're up to date when you return to the app.
While they may improve the user experience, the Post found that the process ends up passing sensitive information onto third-party tracking companies, such as Amplitude, Appboy and Demdex.
The data collected and shared with these companies amounted to 1.5 gigabytes in total, which for some users, can equate to half their monthly data allotment.
Microsoft's OneDrive, Intuit's Mint, Nike, Spotify, the Weather Channel, the Washington Post, Yelp, Citizen and DoorDash are just a few of the many apps whose trackers slurp up large amounts of personal data.
'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?' Patrick Jackson, chief technology officer for privacy firm Disconnect, told the Post.
'I know the value of data, and I don’t want mine in any hands where it doesn’t need to be.'
Read more: How your iPhone harvests your personal data while you SLEEP: Popular apps use hidden trackers to collect emails, IP addresses and other sensitive information without consent