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RE: Action 32 -- Proposed language for site-specific exception

From: Jules Polonetsky <julespol@futureofprivacy.org>
Date: Thu, 10 Nov 2011 06:09:53 -0500
To: "'Aleecia M. McDonald'" <aleecia@aleecia.com>, <public-tracking@w3.org>
Message-ID: <018501cc9f99$46376570$d2a63050$@org>
Studies about self reported user activity around blocking cookies seem to
range widely.  The statistic I cited is based on a review for me by an ad
serving company of their log-files to determine how many users did not have
a cookie from this adserver.  (They have 90 plus per cent reach of the US
population).  Approximately 30 per cent did not have a cookie from this ad
server.

 

So this is because of a number of factors - some users were blocking
cookies, or deleting them upon closing their browser, some may have just
recently cleared cookies, some may have just bought a new computer, or some
may have had so many cookies set that earlier cookies were discarded.  The
takeaway I think is that approximately 30% of users are initially
unrecognized by a third party tracker.

 

From: Aleecia M. McDonald [mailto:aleecia@aleecia.com] 
Sent: Wednesday, November 09, 2011 5:42 PM
To: public-tracking@w3.org Group WG
Subject: Re: Action 32 -- Proposed language for site-specific exception

 

Here I am summarizing a conversation that Rigo, Thomas, Karl, and I had last
week, to share it with the group. 

 

A few notable problems with opt-in cookies are similar to the issues that
make a DNT header attractive in the first place. Namely:

            - Not all user agents support setting cookies

            - Not all user agents are terribly fingerprintable, and these
are often the same as not supporting cookies (for example, a not-so-smart
phone)

            - Many users either block or manage (that is, some how delete)
cookies. In Princeton, Jules suggested this may be something like 40% in the
US and 50% in Europe. This is from memory; I leave Jules to correct me if
I'm off.

            

And for me the biggie:

            - The users who have DNT on (which is a superset of users who
will opt back in) are far more likely to be among the subpopulation of users
who manage their cookies. Designing a solution that is least likely to work
for the population most likely to use it seems like a problem to me.

 

So while I very much agree with Nick that having a standard way to add
site-specific exceptions is highly desirable, I hope we can find a mechanism
that works better than cookies. 

 

            Aleecia

 

On Nov 9, 2011, at 2:26 PM, Nicholas Doty wrote:





One advantage of a tech-specific requirement (placing an opt-in cookie)
would be the relative simplicity for users to clear all of their tracking
opt-ins - just clear your cookies. If some sites use fingerprinting and
other sites use localStorage and yet others use cookies to store a user's
opt-back-in status, then a user would have to manually manage on a
site-by-site basis if they decided they wanted to opt-out again.

 

We might be able to address this concern with some variation of the Tracking
response header / well-known location such that user agents could detect
when a user is being tracked because of an opt-back-in and give the user a
pointer on how to clear it. This is also an advantage of the
user-agent-managed list of site-specific exceptions: the user agent could
make it easy for users to see and modify the list of site-specific
exceptions.

 

Thanks,

Nick

 

On Nov 9, 2011, at 8:14 AM, Shane Wiley wrote:





Thank you John - helpful starting point.  I'd suggest we not assert only a
cookie as the "exception" memory mechanism but a recommended one.  It could
be equally viable and appropriate to store this information in a
registration key, a browser setting, or some other technical mechanism.

 

- Shane

 

From: John Simpson [mailto:john@consumerwatchdog.org] 
Sent: Wednesday, November 09, 2011 8:00 AM
To: Aleecia M. McDonald; Nicholas Doty
Cc: public-tracking@w3.org Group WG
Subject: Action 32 -- Proposed language for site-specific exception

 

Proposed language for a site-specific exception using a cookie:

 

When a DNT enabled user agent grants a site-specific exception, the site
places a site-specific opt-in cookie on the user agent allowing the site to
respond as a First Party.  The DNT header must remain enabled so that if the
user returns to the site, both the user's general preference for DNT and the
site-specific exception will be clear.  This could enable the site to
provide a higher level of privacy than if DNT were not enabled, but less
than if the exception had not been granted. Opt-in site-specific exception
cookies should expire within three months, enabling the site to determine
periodically whether the user intends to continue to grant an exception.

 

----------------

John M. Simpson

Consumer Advocate

Consumer Watchdog

Tel: 310-392-7041

 

 

 
Received on Thursday, 10 November 2011 11:10:27 UTC

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