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Comment by jacquesm | Hacker News Reader

I wonder how Facebook is able to implement the EU privacy directives with this technology as their long term storage solution. If a customer requests deletion of their data you're supposed to comply with that, even on back-ups.

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Delete by forgetting an encryption key.

If you encrypt each users data, in every backup, using a unique key, you need only erase the key in a central database to invalidate all possible backups.

In all seriousness, it is more than likely a flag:

  User.IsDeleted = true

  User.Status = Status.Deleted (or Status.Deactivated)

Facebook allow users to deactivate their accounts, which can then be reactivated. Facebook users can also delete their accounts. Facebook say that this is permanent:

  When you delete an account, it is permanently deleted from Facebook. 
  You should only delete your account if you are certain you never want 
  to reactivate it.

Permanently deleted still doesn't mean deleted. It just means that you can't recover it. Facebook have never publicly stated what their deletion process is.

Is it logical or physical?

Since Facebook keep anonymous profiles, I wouldn't be surprised if deleted accounts just get migrated to anonymous profiles which they can still profit from. That's what I'd do if I was Facebook.

That kind of flag wouldn't be enough to satisfy EU privacy directives, the comment you're replying to is all about.

"Permanently deleted" means exactly what it says. Deactivated means that the account is inactive but the data is still there. When you delete your account the data is gone within 14 days, no options for recovery; it happens in bulk and with a bit of a grace period for 'buyers remorse' so it is somewhere in the tail end of that 14 day period. And yes, Facebook has publicly stated their deletion process on multiple occasions and has explanations of how it works in online help docs and FAQs that you just choose to ignore.

Wow, is that an official FB statement? I need to make a copy of that :)

Thanks for your insights, much appreciated!

He did reference the online help / FAQ:

https://www.facebook.com/help/359046244166395/

FB isn't exactly good at trust when it comes to its users. The whole business is about extracting value from its user base as an asset. Companies normally don't like throwing away assets if they can help it.

Until I see evidence to the contrary, I will assume that FB doesn't delete user data completely. That is just my preference based on the evidence of FB's previous actions. Others can believe what they will. I don't trust the online help docs or FAQs as far as I can throw them. FB has made a business out of abusing user privacy.

  Zuck: Yeah so if you ever need info about anyone at Harvard
  Zuck: Just ask
  Zuck: I have over 4,000 emails, pictures, addresses, SNS
  [Redacted Friend's Name]: What? How'd you manage that one?
  Zuck: People just submitted it.
  Zuck: I don't know why.
  Zuck: They "trust me"
  Zuck: Dumb fucks

Finally, as programmers, we all know how hard it is to remove elements such as a user from a graph. A user is key element of FB. It is challenging to remove a user, since they have a multitude of cross-related information, linked to other users and other user content. Either you delete the user logically and then hide their linked content, or you delete the user physically, but first delete all of the linked content, or you replace the user with a 'deleted user profile' and hide their linked content. Any other ways?

FB obviously hadn't done this back in 2010 [1] and maybe they have been trying hard to fix this issue, but I'd welcome an official post from FB tech team that states how they went about implementing this feature. Maybe a bit of transparency would go a long way in helping the more paranoid of us to think twice about FB.

[1] http://www.zdnet.com/article/facebook-does-not-erase-user-de...

  > Finally, as programmers, we all know how hard it is to
  > remove elements such as a user from a graph.

Yet blocked users do disappear from the graph.

Yet I don't think anyone will ever check that. How are you going to find one picture that should've been deleted in a cold storage system with exabytes of data (trillions(?) of photos)?

Easiest way would be by just using another (slightly more expensive) cold storage medium for EU residents. From the article it sounds like they havent rolled this out to all data (yet)

Assuming each item is scrambled with a small, unique key (kept on hot storage), just throw away the key?

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