(Credit: Valery Brozhinsky/Shutterstock)

In the world of online ads, there are two major types: the generalized kind that's intended to induce demand, and the specifically targeted kind which is supposed to detect a demand and connect that to a sale. For the second kind to be consistently accurate, it needs user data. Apparently, lots and lots of user data. And according to one researcher, sometimes the ad sellers are quite reluctant to let go of the information that they have on you.

In a long post on Medium, an assistant professor at the University of Southern California in the area of computer science documents a voyage with Facebook's location settings that may cure a case of narcolepsy.

SEE: Facebook discloses photo security bug that may have hit up to 6.8 million users

For privacy reasons, she doesn't want the social network to know where she's located or where she's going, so she's diligently disabled all the location tracking features she can find within her phone's operating system, within the Facebook app itself and on Facebook's website, where her profile page deliberately lacks an entry for a place of residence.

According to Facebook, it only serves location-based ads if you let it collect your location history. And the website gives users a tool to completely wipe this history at any time. Therefore, an empty location history log should result in no more location-based ads, right? Unfortunately for Assistant Professor Aleksandra Korolova, this doesn't appear to be working out.

Her attempts to keep her location from Facebook have left few if any stones unturned: "I haven't uploaded photos to Facebook for years, I don't post content tagged with my location or check-in to places. I don't give access to my location to WhatsApp, Instagram or Facebook Messenger. I don't search for places on Facebook. Yet the location-based ads, using my actual locations, keep coming."

As Korolova points out, Facebook's language on the matter is very clear. It explicitly states, "People have control over the recent location information they share with Facebook and will only see ads based on their recent location if location services are enabled on their phone."

So what's going on? Korolova produces an interesting Facebook Business support page, where "passive wifi" is identified as an element separate from your location settings. It's unclear if this refers to an actual type of Wi-Fi technology, or if it's just Wi-Fi data collected in manner that Facebook characterizes as "passive."

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When we spoke to Facebook about the Medium report, a representative said, "Facebook does not use WiFi data to determine your location for ads if you have Location Services turned off. We do use IP and other information such as check-ins and current city from your profile. We explain this to people, including in our Privacy Basics site and on the About Facebook Ads site."

Of course, if Facebook can't see your IP address, it can't deliver content to you. Just like someone can't call you if they don't have your phone number. So Facebook has to have that basic information to provide its services.

However, if it's using your IP address to delivering location-based ads, when you're clearly doing everything within your power to avoid them (and you're evidently informed enough to know every lever that can be pulled outside of Facebook HQ), it may be difficult to reconcile Facebook's public campaign to improve user trust with evidence that Facebook is still sharing your IP address with advertisers, regardless of the privacy settings available to you on your phone or within your social network profile.

Takeaways

  • An assistant professor at USC reported on Medium that Facebook delivered location-based advertising even when she disabled every relevant setting on her device and within her Facebook account.
  • A Facebook representative stated that the social network may still use your IP address to determine your location for targeted ads.

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Tom McNamara is a Senior Editor for CNET's Download.com. He mainly covers Windows, mobile and desktop security, games, Google, streaming services, and social media. Tom was also an editor at Maximum PC and IGN, and his work has appeared on CNET, PC Gamer, MSN.com, and Salon.com. He's also unreasonably proud that he's kept the same phone for more than two years.