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Re: how does host B know that its visitor is the one that visited host A?

From: Paul Libbrecht <paul@hoplahup.net>
Date: Sun, 14 Aug 2011 11:35:35 +0200
Cc: www-tag@w3.org
Message-Id: <79691F29-71C8-4617-A135-E16B06189E14@hoplahup.net>
To: Jonathan Rees <jar@creativecommons.org>
Jonathan,

are you assuming the servers communicate to one another?

One particularly vicious communication would be from such hosts as Google Analytics which sees the URL requests made to a huge amount of servers of the earth (they don't really know the content of the web-page thanks to browser protection but URLs tell a lot). I think Facebook inserts (e.g. badges) are of the same type (because they prevent caching).

If such a communication happens, you have all the solutions to the below experience: your browser is identified with a cookie and that is submitted to the "common" server (analytics.google or facebook).

What would be nice is to find tests to discover these and be able to warn or to blame non-respect of the terms of use. Maybe something is doable.

paul

PS: Privacy libertarians are aware of these but then... many including the EU even say one should reject cookies except explicitly authorized. This is non-realistic for today's architecture. A more nuanced position is needed.






Le 12 août 2011 à 17:11, Jonathan Rees a écrit :

> Probably everyone knows this but me...
> 
> I shop at expedia.com (or somewhere) for a London hotel room. Later I
> visit guardian.co.uk and see an Expedia ad for London hotel rooms.
> 
> I visit guardian.co.uk in a different browser (same computer & IP
> address but Safari instead of Chrome) and instead get an ad for
> magazine subscriptions. Apparently the Guardian can tell my two
> browsers apart somehow - it's using more than just my IP address to
> decide what ads to show me.
> 
> How does this work? I.e. what are browser instances doing that leaks
> their identity to servers? Is it just a lucky guess based on
> User-agent or something?
> 
> (a propos our privacy & tracking discussions)
> 
> Thanks
> Jonathan
> 
Received on Sunday, 14 August 2011 09:36:06 GMT

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