How Facebook Knows When Its Ads Influence Your Offline Purchases

How Facebook Knows When Its Ads Influence Your Offline Purchases(wired.com)

52 points by cyphersanctus 11 years ago | 47 comments

gcb0 11 years ago |

...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.

tzs 11 years ago | |

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?

wdewind 11 years ago | | |

I feel like PG's submarine piece has really made HN's view of PR very black and white. There are a lot more gradations, and likely this is a piece that was pitched by Facebook and actually was moderately investigated by Wired. The worst journalists are copy pasting press releases, the best are finding their own stories, but the vast majority lie somewhere in between. And I'm not convinced there is anything wrong with that.

cpeterso 11 years ago | | |

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.

chestnut-tree 11 years ago |

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 mobile number solely for two-factor authentication and absolutely nothing else? Who knows? Google doesn't tell you.

When you can sign in on your tablet/mobile/desktop/TV/thermostat/fridge and who knows what else - how hard can it possibly be to stitch together your spending and consumption habits with all the other data collected about you? In fact, it wouldn't surprise me if those joined-up journeys have already been compiled. It's pretty obvious that the information companies collect about you goes far, far beyond creating a simple "advertising profile".

Companies like Google and Facebook (and others) have no self-restraint when it comes to tracking you and they don't even do it anonymously. How do they get away with it? Because we happily let them.

dao- 11 years ago | |

Sure. I think the difference is that Google hardly gives you a choice, other than not using their products. Not that this is a great situation. And it still doesn't answer the question why people would give away the same information voluntarily without a direct need.

jfuhrman 11 years ago | |

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.

phatfish 11 years ago | | |

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.

dmurray 11 years ago |

> 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?

logicallee 11 years ago | |

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 everything, because 1-100 (age) M/F (gender) only has 200 possible values. 200 hashes later your counterparty knows what you were asking to check.)

But that doesn't mean this couldn't be done properly.

There are actual zero-knowledge proofs. I liked this primer. You should read it!

http://blog.cryptographyengineering.com/2014/11/zero-knowled...

It is 100% possible for there to exist absolutely zero-knowledge proof in many instances. (Such as the one in the article.)

So, it could be possible for example (I don't know an algorithm) to check whether a phone number you were given is in someone else's set of phone numbers - without either your learning what the other's set is, or the other learning what phone number you're testing.

dmurray 11 years ago | | |

If there is, the 'someone else' would still have to do some rate limiting. Otherwise, once again, I can just run this algorithm for all possible phone numbers.

marco1 11 years ago | | |

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.

moab 11 years ago | |

Why on earth would you have to brute force all numbers? You can do this optimally: just hash the numbers you see (or get requests for).

dmurray 11 years ago | | |

So that I can cold call someone who might be interested in my product, even though DataLogix only told me the hash of their phone number.

phkahler 11 years ago |

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 the sale? Because they honestly don't deserve it. I'm going to buy one anyway and I have not seen an ad for a place I didn't look already. While I often give a real store the business based on "I can get it on the way home" the price difference in this case is nuts. So NewEgg it will be and Facebook ads aren't going to influence that.

In this case, correlation does not indicate causation.

jeffchuber 11 years ago | |

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

phkahler 11 years ago | | |

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

dao- 11 years ago |

"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?)

jankassens 11 years ago | |

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 number, but as far as I can tell, most people give a real number.

It's certainly a different culture in Germany. Media and people are a lot more concerned collection of data.

qq66 11 years ago | | |

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.

berelig 11 years ago | |

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.

anigbrowl 11 years ago | | |

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.

dao- 11 years ago | | |

Same here regarding the postal code, that's fairly common in Germany.

spacefight 11 years ago |

"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.

lozf 11 years ago | |

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.

hnnewguy 11 years ago |

>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 to sell the personalized data. Either or Both of which are inevitable.

All in all, a moderately informative marketing piece.

bitwize 11 years ago | |

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

The stuff about you personally that can be gleaned from market analytics will make you shit a brick.

And this is what private industry can do, not even getting into three-letter agencies.

cpeterso 11 years ago | |

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

Facebook wants to keep the data inside their keep.

notahacker 11 years ago |

tldr; it doesn't, but offline vendors that collect your contact information they can anonymously check the proportion of purchasers which might [incidentally?] have been shown their ad on Facebook's network. Only a media buyer with a budget bigger than their brain would assume causality.

jessriedel 11 years ago | |

Couldn't Facebook easily demonstrate causality by running an RCT? Just randomly select half of a certain demographic to show the ad to, and then show that those users are more likely to make a purchase later.

notahacker 11 years ago | | |

Theoretically yes, but I think with standard Facebook ad units and regular consumer brands sold in stores they'd be pretty unhappy with the results...

(since probability of giving stores your contact details post purchase and susceptibility to marketing messages pre-purchase are probably positively correlated and Facebook is permanently running concurrent trials of different kinds and being very selective about what they share, any positive effect they did manage to identify should be viewed as an almost certain overstatement of the ads' actual effectiveness anyway)

chiph 11 years ago |

Who gives their phone number to store clerks? "Sorry, it's unlisted."

breitling 11 years ago | |

As hard as it is to believe, I'm sure plenty of people give out their phone numbers when asked. I have personally witnessed many many people (including my wife) give out their number at checkout without hesitation. I guess the fact that this is continued practice means that it actually works.

This may vary by geography...my observations are from Canada.

prostoalex 11 years ago | |

Large department stores would frequently pitch a loyalty card that's then tied up to your profile, for a which a phone number is frequently a must.

sp332 11 years ago | |

It's s numbers game. If store clerks ask everyone, all the time, then enough people will answer for the practice to be useful.

oliyoung 11 years ago | |

I'd argue that any HN member (or even any 1/2 tech savvy consumer) isn't exactly their target market

idiotclock 11 years ago |

Is anyone else frightened the increasing efficiency of capitalism? Since when does user-experience depend on best fulfilling my consumer desires? Shouldn't I try to soften this impulse?

song 11 years ago |

And this is why I did not give my phone number to facebook and why I use a different email for everything.

It's unfortunate that keeping one's privacy requires a lot of knowledge and work.

polynomial 11 years ago | |

> It's unfortunate that keeping one's privacy requires a lot of knowledge and work.

I wonder if the more vexing problem is that the market for privacy solutions seems largely unproven at scale. While people seem to value privacy when polled individually, they seem to vote the other way as an aggregate body.

Smart privacy products could take the knowledge and work out of it, but will the market support them?

cornewut 11 years ago |

Amazon product pages already have Facebook tracker embedded, so Facebook knows what you are looking at. No need to provide your phone number.

walterbell 11 years ago | |

Is that visible via NoScript?

cornewut 11 years ago | | |

I'm using disconnect.me

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.