Facebook targets ads using phone numbers submitted for 2FA

If you sometimes wonder – or often – how or why you see some online advertising, here is a possible answer.

Most Facebook users know that the company targets ads based on information they willingly give to the company, but the researchers also found that the social media giant also targeted ads that users did not know they targeted them. l & # 39; company.

For example, phone numbers provided for two-factor authentication are also used to target ads on Facebook, according to a new report citing a study entitled "Study of IPI sources used in Facebook's targeted advertising" by northeastern and Princeton researchers. the universities.

When a user gives Facebook a phone number for two-factor authentication or to receive alerts on connections, "this phone number can be targeted by an advertiser in a few weeks," Gizmodo said.

A spokesman for the company told Gizmodo that "we use the information provided by people to offer them a more personalized experience, including more relevant ads."

However, the study also shows – and Gizmodo has tested, successfully targeting an ad on a computer teacher using a landline number – that Facebook's user contacts can be targeted without their consent. Facebook users who share their contacts expose these contacts to potential targeting.

This means that, as a Facebook spokesman told Gizmodo: "We understand that in some cases it may mean that another person will not be able to control the contact information that someone else has. one on the other downloads about it.

A spokesman for Facebook told the news agency on Thursday: "We clearly know how we use the information we collect, including the contact information that people download or add to their own accounts. You can manage and delete the contact information you have downloaded at any time.

In the study, the researchers said that the use of such information by Facebook was predictable, since this is the business of the company. "This incentive is exacerbated by the recent introduction of IP-based targeting, which allows advertisers to specify exactly which users to target by specifying a list of their PII," they said.