Maybe check your data archive to see if Facebook’s algorithms know who you called. [Update, March 25, 2018, 20:24 Eastern Time]: Facebook has responded to this and other reports regarding the collection of call and SMS data with a blog post that denies Facebook collected call data surreptitiously. The company also writes that it never sells the data and that users are in control of the data uploaded to Facebook. This “fact check” contradicts several details Ars found in analysis of Facebook data downloads and testimony from users who provided the data. More on the Facebook response is appended to the end of the original article below.
This past week, a New Zealand man was looking through the data Facebook had collected from him in an archive he had pulled down from the social networking site. While scanning the information Facebook had stored about his contacts, Dylan McKay discovered something distressing: Facebook also had about two years’ worth of phone call metadata from his Android phone, including names, phone numbers, and the length of each call made or received.
In response to an email inquiry by Ars about this data gathering, a Facebook spokesperson replied, “The most important part of apps and services that help you make connections is to make it easy to find the people you want to connect with. So, the first time you sign in on your phone to a messaging or social app, it’s a widely used practice to begin by uploading your phone contacts.”
The spokesperson pointed out that contact uploading is optional and installation of the application explicitly requests permission to access contacts. And users can delete contact data from their profiles using a tool accessible via Web browser.