The hidden perils of cookie syncing | Hacker News Reader

The hidden perils of cookie syncing

freedom-to-tinker.com

63 pointsrandomwalker15 comments

Web users strike me mostly as naive idiots. It's like they suddenly looked up and are shocked, shocked! that all the free stuff on the internet they enjoy: high quality journalism like nyt or verge, gossip like gawker, games, free email + calendar + video services, free chat, free social network services, an excellent search engine, and on and on and on, actually required money to build and run! And that the companies involved are going to go to great lengths to earn as much advertising money as possible. You have to seriously be an idiot to think that all these companies building services that end users don't pay for aren't making money off the end users. Users had to choose between privacy/paying for things and free stuff, and they clearly chose free stuff.

It's definitely not the choice I would have made, but I got massively outvoted.

Web users are fairly naive. Most don't recognize ads in Google results, at least as of 2012.

I wouldn't even say that it's a function of maximizing ad revenue. If you wanted to maximize ad revenue, you'd run Google Ad Exchange, not, say, media.net or AdSense. AdX actually has reasonable policies around cookie syncing. Website operators do many things poorly as far as revenue optimization goes--invading my privacy is not step one for them to increase revenue.

The really big players are sensitive to the PR backlash and behave somewhat reasonably. The people out of the limelight do the really sneezy things. I think it is reasonable that most people do not expect hundreds of third parties to have their browser history dating back several years. Perhaps you trust the NYT to know your political leanings, but you don't expect that data to leak to third parties.

On AppNexus, you can buy pixel segments of users with certain diseases. That's fine, if a little creepy, until you think about how easy it would be to deanonymize that data.

Even very trustworthy actors get this wrong, btw. The government of Ontario's human rights website was, until recently, pixelling every visit to their site courtesy of the ShareThis widget, including sensitive topics like transgender rights. There was no profit motive there, just oversight on the government's dev team.

Is it naive to expect that when you visit a government page about transgender rights, you won't be added to a list of people presumed to have gender dysphoria, which a third party then sells to other third parties?

Curious people may want to research "data leakage", which is a developing field in the ad ops world to prevent some of these harmful scenarios.

I have used the add-on "Self-Destructing Cookies"* to handle normal cookies, with only a few non-tracker web sites on my whitelist. It has been surprisingly non-intrusive. It works by removing all cookies from domains that have not been visited for (by default) ten seconds, resulting in very few cookies lying around. I am not aware of an equivalent add-on for non-Firefox browsers.

* https://addons.mozilla.org/en-US/firefox/addon/self-destruct...

Thanks for the tip! I went through my entire cookie list (accessible from the Firefox options dialog) and went from hundreds of domains to ~10 whitelisted ones. I was baffled to see how many cookies I had stored that I didn't even know about.

They should call that "baking paper": cookies just slide off you! :)

Both firefox and chromium have an option to disable third-party cookies. I believe this stops this sort of tracking, making each webpage a silo.

I additionally isolate websites where I need to log in into their own profile using a shell script for each along the lines of the following:

    chromium-browser --app=http://facebook.com/ --user-data-dir=/home/jewel/work/facebook-profile

I'm one of the authors of the paper. One of our findings was that third-party cookie blocking is only marginally effective. See the tables under cookie syncing in our summary [1] or in our full paper [2]. Trackers bypass cookie blocking in a variety of creative ways. We're currently investigating the bypassing mechanisms in more detail.

On the other hand, add-ons like Ghostery work much better.

[1] https://securehomes.esat.kuleuven.be/~gacar/persistent/index...

[2] https://securehomes.esat.kuleuven.be/~gacar/persistent/the_w...

People need to stop promoting Ghostery. It's made by Evidon, yet another tracking company. Just checkout their website and it's clearly obvious that everyone that installs this extension is doing them a huge favor:

https://www.ghosteryenterprise.com/

It's identical to the adware companies that promise to help remove adware from your computer... but for some reason people keep using it!

Slightly off-topic but something with my Iceweasel/FF install (v31) borks the layout of the blog completely -- content is shifted far to the right of the viewport for some reason. Looked fine on another computer, so not sure what's up. Also works fine in chromium. FYI.

Can you summarize for us how to avoid this kind of tracking? Is there much we can do besides Ghostery?

I block tracking at the domain level via a custom hosts file: http://someonewhocares.org/hosts/

Actually, I went one step further than this, I dump that hosts file into dnsmasq and set that as my primary domain controller for the home network. So anything connected via WiFi or ethernet (phones, tablets, laptops, etc) will also have tracking blocked.

A belated thanks. Much appreciated.

Third party cookie blocking on all modern browsers is a joke. I turn third party cookies off as a start, but sites can play all kinds of games with cookies to create "first party" relationships you don't know about, and that's not even including things like flash cookies or browser fingerprinting.

As a start, consider that if you turn off third party cookies, logging into gmail also logs you into youtube.com. Yes, both are owned by the same company, but they are clearly different domains and so youtube should be a third party in your transactions with gmail.

> As a start, consider that if you turn off third party cookies, logging into gmail also logs you into youtube.com. Yes, both are owned by the same company, but they are clearly different domains and so youtube should be a third party in your transactions with gmail.

That's because you don't sign into youtube, you go through Google's single sign on stuff which is a different domain.

Check again. The two sites are on different domains. In order to log into both, at some point someone needs to convey state information to a third party. Gmail logins are managed through accounts.google.com, so either you have a third-party relationship with accounts.google.com when you are on youtube.com, or you have a third party relationship with youtube.com when you are on accounts.google.com. Either way, you pick up a third party cookie.

You'll notice that even if you never (deliberately) went to youtube and you have 3rd party cookies turned off, a cookie for "youtube.com" will show up when you sign in. I haven't looked at it carefully, but I think they just put you through a chain of redirects when you click "log in" so that you have a first party relationship with each of the domains they want to sign you in to, and that's when they give you the cookie.

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