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Ask HN: How does Facebook know what I buy on Amazon or vice versa?

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Re: Ask HN: How does Facebook know what I buy on Amazon or vice versa?

#91

Post by danilocesar »

Not totally related to the post, but IMHO the following happen too often:

I'm looking for a camera. So I opened a market place in my country that sells those cameras. Then I decided to buy one.

Then, for a few days, I open facebook and I only see ads about cameras, from the same marketplace. That's useless as I'm sure (and they should know with some confidence) I'm not buying another camera. They should/could target me ads about SD cards, lens. But certainly not cameras.

* Then it happened again when I bought the SDCards =/

Re: Ask HN: How does Facebook know what I buy on Amazon or vice versa?

#92

Post by Grustaf »

I read your question as being about how facebook found out from amazon what you bought. I don't know much about web technology but it seems to me they don't need to know, since the ads you mentioned came from Amazon, even if they're served inside facebook. So it's enough if facebook gives enough info to amazon so that the latter can infer who you are, then they know that you bought that bike.

It's somewhat encouraging that the algorithms are still so stupid as to advertise precisely the things you are least likely, a large infrequent purchase that you just made!

Re: Ask HN: How does Facebook know what I buy on Amazon or vice versa?

#96

Post by mrhektor »

On a related note, I had a weird experience where I was talking about a trip to Vietnam with my friends. A few hours later, I saw an ad for air travel to Vietnam on my FB page.

Now I'm 100% sure I hadn't googled or searched for Vietnam previously. At first, the conspiracy theorist inside said "they're listening!" through my phone microphone or whatever. But then, I thought, could they have been forming a pattern of my behaviour over the past several days, cross-referenced across several platforms (maybe I had searched for "Travel destinations" and also a friend had given a travel recommendation of Vietnam on chat)? Have the algorithms gotten that advanced?

Re: Ask HN: How does Facebook know what I buy on Amazon or vice versa?

#97

Post by MichaelGG »

Grustaf wrote: post #92

I read your question as being about how facebook found out from amazon what you bought. I don't know much about web technology but it seems to me they don't need to know, since the ads you mentioned came from Amazon, even if they're served inside facebook. So it's enough if facebook gives enough info to amazon so that the latter can infer who you are, then they know that you bought that bike. It's somewhat encouragin…

Are they stupid? I've cancelled and bought a competing product more than once, though not via ads (adblocker), just searching or reconsidering.

Re: Ask HN: How does Facebook know what I buy on Amazon or vice versa?

#98

Post by kristianc »

Amazon has a Facebook retargeting pixel loaded which identifies you based on your (probably logged in but quite possibly not) Facebook account. Facebook has you IDed across browsers and across devices, getting around the single browser limitations cookies usually have.

This links back to your FB account. Best practice would be for advertisers to also load a 'burn' pixel on a conversion page which lets them know you have purchased the product, but the tech doesn't always allow for this.

Re: Ask HN: How does Facebook know what I buy on Amazon or vice versa?

#99

Post by MichaelGG »

reaktivo wrote: post #14
TekMol wrote: post #9

I have had similar experiences. Others have already mentioned some cross-browser fingerprintig techniques. One of the worst that many people don't know about is that browsers hand over your local IP. Check this proof of concept: http://net.ipcalf.com/ The media device IDs the browsers provide look even worse: https://jsfiddle.net/u4n4s296/ I am not sure if these are unique to the device type (for example a certain so…

Whoa, for a moment I felt pretty sure you would be mistaken. Hadn't read about this particular vulnerability before.

WebRTC leaks have been known, and the WebRTC or Firefox people said they'd disable peer to peer data channels off if this technique became used for tracking. Because a permission prompt was too much. WebRTC folks couldn't even come up with a real use case for silent data channels.

Re: Ask HN: How does Facebook know what I buy on Amazon or vice versa?

#100

Post by 0xcde4c3db »

mrhektor wrote: post #96

On a related note, I had a weird experience where I was talking about a trip to Vietnam with my friends. A few hours later, I saw an ad for air travel to Vietnam on my FB page. Now I'm 100% sure I hadn't googled or searched for Vietnam previously. At first, the conspiracy theorist inside said "they're listening!" through my phone microphone or whatever. But then, I thought, could they have been forming a pattern of m…

> Now I'm 100% sure I hadn't googled or searched for Vietnam previously.

I'll bet your friends did.

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