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How Facebook Knows When Its Ads Influence Your Offline Purchases

wired.com

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Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#41

Post by marco1 »

logicallee wrote: post #10
dmurray wrote: post #6

> The trick is that the hash of a phone number captured on Facebook will look just like the hash of the same phone number captured in a brick and mortar store, so the two companies can match the numbers without actually trading them. This just isn't possible. How many cents would it cost to brute-force hash all legal American phone numbers?

This is correct. As a zero-knowledge proof it is, sadly, trivially broken. (Not just in a theoretical sense. As you mention there just isn't enough entropy going into the hash. It's like asking for your age and gender, but only providing a hash to some other party so they can verify that you are who you say you are, without your divulging what information you were just given. That doesn't work - you would leak everyt…

Many other apps hash phone numbers to "suggest" security and privacy as well, e.g. Secret. Other apps don't even bother to create the hashes and send the plain text phone numbers, e.g. WhatsApp.

Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#42

Post by cpeterso »

hnnewguy wrote: post #3

> As Boland explains it, Facebook simply shows advertisers that a given number of people who saw an ad for a product also purchased that product. Facebook doesn't share my personalized shopping data with advertisers. That's good. But the data still exists. So the data the advertisers receive is only really anonymous until there's some sort of security breach or economic decision whereby it's suddenly more profitable…

> Facebook doesn't share my personalized shopping data with advertisers. That's good.

Facebook wants to keep the data inside their keep.

Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#43

Post by cpeterso »

tzs wrote: post #26
gcb0 wrote: post #2

...aaand facebook starts to buy news pieces to justify their ad network. this is nothing more than a press-release for their atlas feature. A new low even for wired.

Odd. It seems unusual for a press release to include criticism from the EFF. How would the article have to have been written for you to not think it was a press release?

Criticism? The EFF comments were practically praising Facebook:

  From the outside, says Adi Kamdar, an activist with the Electronic Frontier
  Foundation, it seems Facebook is “doing a good job” anonymizing personal
  info as it seeks to link online and offline behavior. Facebook is adamant
  that its system can’t be cracked—i.e. can’t be used to match names from
  Facebook accounts with behavior off of Facebook—and Kamdar says he has no
  reason to believe otherwise.

Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#44

Post by qq66 »

jankassens wrote: post #33
dao- wrote: post #14

"It has happened to you, and it has probably happened more than once." Umm, no. Why on earth would I give my phone number or email address to random shops? This is crazy. I surely don't want merchants to contact me "about other stuff I might want to buy." This assumption sold as a certainty in this article is somewhat disturbing. Do others from the US feel the same way? (I'm from Germany. Different culture?)

Store memberships for points and rebates on products are really common here in the US. When you sign up for them, they ask for your email, phone number, address, etc. Safeway, a big supermarket chain, does this to an extreme. Many of their products are "50% off" when you enter your phone number of your membership on checkout. (It really just brings it down to a normal price). Nothing prevents you from using a fake nu…

I use a fake number and a fake name at Safeway, and they always address me by the fake "Mr. XXX" when I check out. Always a little weird.

Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#45

Post by lozf »

spacefight wrote: post #9

"People voluntarily link things like phone numbers and email addresses to their Facebook accounts" People voluntarily are idiots. Never connect a phone number to your FB account and use another mail address if you really need to have an account.

I agree with you, but sadly it's not that straightforward; It's entirely plausible (perhaps even likely) that your "facebook friends" have your number, and do something stupid^H^H^H^H^H^Hconvenient like give fb access to their address book (as is often requested, and I wouldn't be surprised if it happens by default with their mobile apps), Facebook are only one name match away from having your number and perhaps DoB and other personal info anyway.

Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#47

Post by mgbmtl »

anigbrowl wrote: post #29
berelig wrote: post #16

Earlier quoted context omitted.

I can only think of a couple of retailers that have asked me for an email address here in Canada (coincidentally both were US companies). I do get asked for my postal code fairly often but that's hardly a personal detail.

You postal code, name and the expiration date on your card is enough to positively ID you in many consumer databases, and by giving it to the retailer you're implicitly granting consent for its use for this purpose.

I am not a lawyer, but I'm pretty sure that in Canada, this would be in violation of the federal "Personal Information Protection and Electronic Documents Act", as well as many provincial laws.

https://www.priv.gc.ca/leg_c/leg_c_p_e.asp

"Use or disclose personal information only for the purpose for which it was collected, unless the individual consents, or the use or disclosure is authorized by the Act."

"Keep personal information only as long as necessary to satisfy the purposes."

If the client uses one of those "points" cards, yes, they are tracked, but otherwise they shouldn't. When a retailer asks for your postcode, it is mostly just for market study to identify where their clients live, but that's it (although I rarely get asked). You can also just answer "no thanks" to this question.

Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#48

Post by phatfish »

jfuhrman wrote: post #34
chestnut-tree wrote: post #21

Some commentators in this discussion question why anyone would give their phone number to shops when they make a purchase. Yet millions of people give their mobile phone number (and name, date-of-birth and gender) to Google when they sign up for a Google account. And yet the degree of tracking that Google can undertake is an order of magnitude greater than what any individual store can track. Does Google use your mob…

Google uses Android phones GPS location to track people's store visits. http://digiday.com/platforms/google-tracking/ http://www.datadrivenbusiness.com/google-quietly-testing-off... If you turn it off, things like Google Now stop working.

Yep, im pretty sure just the mac address collection from wifi radios would be enough to track what store you have been in if you run an Android phone.

I have wifi and gps turned off except when i am lost.

Re: How Facebook Knows When Its Ads Influence Your Offline Purchases

#49

Post by phkahler »

jeffchuber wrote: post #39
phkahler wrote: post #38

I see false positives. So last week I decided to do my first project that will use a Raspberry Pi. I googled around to the pi site, amazon, newegg, (gasp) radio shack, microcenter, etc... I figured out what I wanted to get but didn't put anything in any carts. So then Pi ads start showing up on Facebook. IIRC a Radio Shack Pi ad too. Whatever. But now when I buy one, is Facebook going to claim some responsibility for…

causation is implied on a population through test and control. causation and correlation for an individual is almost always impossible.

So are they going to use statistical models to figure out how much to charge for ads? That seems like a hard sell.
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