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If I'm reading the actual paper correctly, they looked at Nielsen data from 2016 and figured out that FB trackers fire for a large percentage of web traffic for

If I'm reading the actual paper correctly, they looked at Nielsen data from 2016 and figured out that FB trackers fire for a large percentage of web traffic for both FB users and non-users. Their conclusion is that it's likely FB has the data to be able to build shadow profiles, not that they have any indication FB actually does build shadow profiles. I would be curious about an update based on newer data. 6 years later, even more traffic is mobile where privacy protection is stronger and GDPR has companies more concerned about data sharing and trackers. I'm sure if you included mobile traffic, the trend over time is dropping (with a big dip when iOS 14 came out).

romanhn 5y ago
Yeah, I was really curious about the current state of things, but lost interest after reading the abstract, which was very careful to use "may" everywhere. It's quite a leap to go from "they could do X if they wanted to" to "they're doing X". FWIW, when I worked at Facebook the internal narrative was that shadow profiles were not a thing. Given that everyone had access to source control, one would think any enterprising engineer could easily contradict this, but I don't recall it being actively questioned internally (while many of the company's policies were).
- disgruntledphd2 5y ago
  Man, i hate finally admitting this on HN, but I spent a bunch of years as an FB employee, as a data scientist (on ads). I can speak with complete sincerity and say that shadow profiles were not a thing, and were never a thing during or before my time (before, I can't be 100% certain, but I schlepped through the repos and never found examples of same). What generally happens is that you pick a userid (maybe zero for arguments sake), and everyone who doesn't match to an FB userid gets that number. It didn't make it impossible to build an individual profile, but it made it much, much, much more difficult and I never saw anyone do it. I left in 2018, and would be massively surprised if anyone had built this since. Now, it is entirely possible that not everyone was as rigorous as removing userid=0 (for example) and so some FB data probably counts them, and they may be in some of the clustering models but the notion that they have profiles indexed by browser/device id is completely false (for ads at least, some of the crap they did for PYMK was insane).
- deleted 5y ago
  [deleted]
netsharc 5y ago
Zuck was asked about shadow profiles during his congress hearing. He replied "I'll have to get back to you on that, senator.". There is also "Your off-Facebook activity" (I guess depending on jurisdiction) which shows me online stores that uploaded my data to FB for ad targetting purposes, sadly I use the same "junk" email for online shops and Facebook, and FB's page showed me a lot of businesses who gave it my data!
- disgruntledphd2 5y ago
  > Zuck was asked about shadow profiles during his congress hearing. He replied "I'll have to get back to you on that, senator.". I'm pretty sure that you could ask Mark about loads of existing ads products at FB and he would say the same thing, as he basically delegated all of ads to other people.
- kleinsch 5y ago
  Businesses gave FB data that matched an email with a valid FB profile, so they stored the data and expose it to you in OFA. That's not shadow profiles, that's exposing the info they collected for your real profile.

romanhn 5y ago

Yeah, I was really curious about the current state of things, but lost interest after reading the abstract, which was very careful to use "may" everywhere. It's quite a leap to go from "they could do X if they wanted to" to "they're doing X". FWIW, when I worked at Facebook the internal narrative was that shadow profiles were not a thing. Given that everyone had access to source control, one would think any enterprising engineer could easily contradict this, but I don't recall it being actively questioned internally (while many of the company's policies were).

disgruntledphd2 5y ago
Man, i hate finally admitting this on HN, but I spent a bunch of years as an FB employee, as a data scientist (on ads). I can speak with complete sincerity and say that shadow profiles were not a thing, and were never a thing during or before my time (before, I can't be 100% certain, but I schlepped through the repos and never found examples of same). What generally happens is that you pick a userid (maybe zero for arguments sake), and everyone who doesn't match to an FB userid gets that number. It didn't make it impossible to build an individual profile, but it made it much, much, much more difficult and I never saw anyone do it. I left in 2018, and would be massively surprised if anyone had built this since. Now, it is entirely possible that not everyone was as rigorous as removing userid=0 (for example) and so some FB data probably counts them, and they may be in some of the clustering models but the notion that they have profiles indexed by browser/device id is completely false (for ads at least, some of the crap they did for PYMK was insane).
deleted 5y ago
[deleted]

netsharc 5y ago

Zuck was asked about shadow profiles during his congress hearing. He replied "I'll have to get back to you on that, senator.". There is also "Your off-Facebook activity" (I guess depending on jurisdiction) which shows me online stores that uploaded my data to FB for ad targetting purposes, sadly I use the same "junk" email for online shops and Facebook, and FB's page showed me a lot of businesses who gave it my data!

disgruntledphd2 5y ago
> Zuck was asked about shadow profiles during his congress hearing. He replied "I'll have to get back to you on that, senator.". I'm pretty sure that you could ask Mark about loads of existing ads products at FB and he would say the same thing, as he basically delegated all of ads to other people.
kleinsch 5y ago
Businesses gave FB data that matched an email with a valid FB profile, so they stored the data and expose it to you in OFA. That's not shadow profiles, that's exposing the info they collected for your real profile.