Facebook can use people’s phone numbers to target adverts at them even when they have never handed said numbers over to the company.
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.
The research lays bare 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.
That means that even if a person does…