Deanonymity Reanonymity

It is easy to expose users' secret web habits, say researchers
July 2017, BBC News

"Two German researchers say they have exposed the porn-browsing habits of a judge, a cyber-crime investigation and the drug preferences of a politician." -BBC

This isn't news. (So why am I writing about it?)

Despite what you might think, there is really no such thing as anonymous data, that is, when you have enough data.

Four data points is all it takes to identify or de-anonymize anonymous data, and this goes back to 2006. In other words, if I were to take a bunch of people and assign them serial numbers instead of their names and track every website they went to, all I would need is four websites from one particular serial number, and I would be able to identify who that individual is.

We forget so easily, but over ten years ago, AOL released a bunch of search data, and then took it back down the same day. They realized that you could pretty easily, no, very easily identify, or re-identify the people behind the search data. Then there was a competition to prove it, done on Netflix users, then Twitter users. Now, ten years later, we have already forgotten. Or perhpas, a tech writer at BBC is just looking for clicks. Or maybe he's just tyring to remind us.

There is no privacy on the internet.

On a positive note, your mom was right, you are special and unique and there's nobody else in the world exactly like you (and that's why it's so easy to re-identify your anonymized self).


Notes:
AOL subscribers sue over data leak
Ars Technica, 2006

AOL Proudly Releases Massive Amounts of Private Data
Tech Crunch, 2006

How hard is it to 'de-anonymize' cellphone data?
MIT News, 2013

Unique in the Crowd: The privacy bounds of human mobility.
Yves-Alexandre de Montjoye, César A. Hidalgo, Michel Verleysen & Vincent D. Blondel. Scientific Reports 3, Article number: 1376 (2013). doi:10.1038/srep01376

The official paper:
Paul Ohm. Broken Promises of Privacy: Responding to the Surprising Failure of Anonymization. UCLA Law Review, Vol. 57, p. 1701, 2010
U of Colorado Law Legal Studies Research Paper No. 9-12.
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