Facebook Buys Sensitive Data about its Users to Offer Marketers Increasingly Specific Targeted Advertising

by Vins
Published: Updated:

Julia Angwin, Terry Parris, Jr., and Surya Mattu report that, since 2012, Facebook has been buying sensitive data about users’ offline lives from data brokers and using this information in combination with the data it collects about users. In turn this allows Facebook to sell the information to advertisers who seek to target specific types of Facebook users for their products and services. As they described in an earlier, September 2016 report for ProPublica, “We found Facebook offers advertisers more than 1,300 categories for ad targeting—everything from people whose property size is less than .26 acres to households with exactly seven credit cards.”

Their December report quoted Jeffrey Chester, executive director of the Center for Digital Democracy, “They are not being honest… Facebook is bundling a dozen different data companies to target an individual customer, and an individual should have access to that bundle as well.”

Facebook collects information on users through many clever ways, not just on the likes one provides. Many sites have a Facebook like button option on their page, even if this button is not clicked on, Facebook is able to track that the page was visited—linking back to the user. The data brokers that Facebook works with can also track information through loyalty cards, mailing lists, public records information (including home or car ownership).

Facebook seeks to puts users at ease by providing an opt-out option. However, this requires personally opting out from the six data brokers that sell to Facebook, such as Datalogix or Axciom. As Angwin, Parris, Mattu reported, when they set out to explore Facebook’s opt-out option, they found that some of the data brokers required the last four numbers of a social security pin or another form of identification to disconnect from these tracking capabilities. As they reported, in 2013, reporter Julia Angwin tried to opt out from as many data brokers as she could. 65 of the 92 brokers she found required her to submit some form of identification. “In the end, she could not remove her data from the majority of providers,” despite the fact that she had not signed up for any of these tracking services herself.

ProPublica gathered data for its report on Facebook’s data collection processes by asking Facebook users to share with ProPublica the categories of interest that the site assigned to them. ProPublica collected more than 52,000 unique attributes that Facebook has used to classify users.

The ProPublica report on Facebook’s ad categories is the first of ProPublica’s four-part Black Box series, which explores the power of algorithms in our lives.

Although Facebook’s methods of collecting data about the platform’s users have received corporate coverage, this reporting has not explained the specific tactics used or the information obtained by the companies. For instance, a 2010 Wall Street Journal article described how Facebook reported “it had placed some developers on a six-month suspension from its site” because “a data broker” had “been paying application developers for identifying user information.” By contrast, ProPublica’s 2016 reports suggest that this practice is now systemic and, apparently, acceptable to Facebook.


Julia Angwin, Terry Parris, Jr., and Surya Mattu, “What Facebook Knows about You,” ProPublica, September 28, 2016, https://www.propublica.org/article/breaking-the-black-box-what-facebook-knows-about-you.

Julia Angwin, Terry Parris, Jr., and Surya Mattu, “Facebook Doesn’t Tell Users Everything It Really Knows About Them,” ProPublica, December 27, 2016, https://www.propublica.org/article/facebook-doesnt-tell-users-everything-it-really-knows-about-them.

Student Researcher: Jonnie Zambrano (Citrus College)

Faculty Evaluator: Andy Lee Roth (Citrus College)