An IT teacher noticed Facebook was still posting localized ads even though her phone's GPS was off for this application. In investigating, she realized that Facebook has other ways to achieve this.
"The Location Controls provided by Facebook give an illusion of control over the data that informs one’s ad experience, not actual control. Moreover, Facebook makes false claims about the effect of controls. This statement - which has the merit of being clear - was made by Aleksandra Korolova, assistant professor of computer science at the Southern California University.
In an article published on Medium, she is surprised to continue to see Facebook’s advertisements based on her geographical position while she has disabled Facebook geolocation. She goes even further since she explains that her profile does not contain the city where she lives, that she has not posted a photo on Facebook for years and that she never publishes content containing her position.
Nothing in his behavior betrays his position
She has even disabled geolocation on third-party apps such as WhatsApp, Instagram or Messenger. Finally, she never searches for a geographical criterion in the Facebook application.
So how is it possible that Aleksandra Korolova sees geolocated ads of Santa Monica, the city of California where she lives, and of Los Angeles where she works?
Why did she see ads for activities in Montana while she was crossing Glacier National Park in that state? And why did she see the same kind of geolocated ads when she went to Massachusetts or Israel?
Facebook has many other ways that the only GPS
One could almost believe that this computer scientist is paranoid, except that her doubts are well and truly proven. By going to the "About Facebook Ads" section, she first notes that the social network specifies that the users’ location is also determined by "where you connect to the Internet."
But things go even further when you consult the documents made available to advertisers. A diagram details the processes used by Facebook to measure visits to stores. In addition to the classic geolocation by GPS (which is disabled by Aleksandra Korolova), we see that Facebook collects the Wi-Fi networks that are around the user but also Bluetooth, which can be detected by beacons arranged in the shops.
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IP addresses provide valuable clues
With these data, including connection IP addresses, Facebook does not need more to extrapolate a relatively accurate position, although the geolocation of his device is disabled.
"We use the IP and other information like check-ins or the city mentioned in your profile," confirmed a Facebook spokesperson to Gizmodo. There is no way to completely disable the location for ads.
Now You Know! If we thought we were hiding our location to Facebook, We Were Wrong. The social network has always a way to know more or less your position. Without forgetting the information that the New York Times revealed 2 weeks ago: how Facebook shares users' data with its customers, to the point where it can read private messages….
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