A new study has revealed the extent to which Facebook is furnishing advertisers with so-called “shadow” contact information to enable the targeting of ads via indirect means.
A new report from Gizmodo explains that a team of computer scientists was able to reach individuals using phone numbers and email addresses that they had not shared with the social network.
To prove this, Gizmodo tried to place a targeted ad via Facebook’s “custom audiences” feature. Gizmodo used a landline number for computer science researcher Alan Mislove’s office to place an ad targeting that number and found that the researcher saw the ad within two weeks.
Mislove had never shared that landline number with Facebook, so it’s very likely that Facebook obtained that from the address books of other users who shared their contact information and had the number listed as Mislove’s.
The research reveals the extent of Facebook’s “shadow profiles” — extra data the company collects on users and which it will not reveal that it holds because the information technically belongs to someone else.
Shadow contact details are harvested from other Facebook users who share their phone’s address books with the company so that it can automatically recommend new friends.
The report also points out that a group of researchers from Princeton University have published a paper that delves deeper into these “custom audiences” for targeted Facebook ads, finding that the social network even allows advertisers to target you via the mobile phone number you provided for security purposes.
Facebook didn’t reject the study’s findings, with a spokesperson explaining via email: “We use the information people provide to offer a better, more personalized experience on Facebook, including ads. We are clear about how we use the information we collect, including the contact information that people upload or add to their own accounts. You can manage and delete the contact information you’ve uploaded at any time.”
Facebook’s newest scrutiny comes just months after the Cambridge Analytica scandal, which saw some 87 million users’ data being harvested and shared with the Trump-affiliated research firm without their knowledge.