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blog: Don Marti

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Welcome. How is everyone's tracking protection working?

26 March 2017

This is a brand new blog, so I'm setting up the basics. I just realized that I got the whole thing working without a single script, image, or HTML table. (These kids today have it easy, with their media queries and CSS Grid and stuff.)

One big question that I'm wondering about is: how many of the people who visit here are using some kind of protection from third-party tracking? Third-party tracking has been an unfixed vulnerability in web browsers for a long time. Check out the Unofficial Cookie FAQ from 1997. Third-party cookies are in there...and we're still dealing with the third-party tracking problem?

In order to see how bad the problem is on this site, I'm going to set up a little bit of first-party data collection to measure people's vulnerability to third-party data collection.

The three parts of that big question are:

  • Does first-party JavaScript load and run?

  • Does third-party JavaScript (from a site on popular filter lists) load and run?

  • Can a third-party tracker see state from other sites?

This will be easy to do with a little single-pixel image and the Aloodo tracking detection script.

Step one: add an image and two scripts to the page footer

This blog is on Metalsmith, so the right place to put these scripts will be in layouts/partials/footer.html.

The lines that matter are:

<script src="/code/check3p.js"></script>
<script src="https://ad.aloodo.com/track.js"></script>
<img id="check3p" src="/tk/sr.png"
 height="1" width="1" alt="">

I'm including a single-pixel image and two scripts: the Aloodo one and a new first-party script.

In most tracking protection configurations, the Aloodo script will be blocked, because ad.aloodo.com appears on the commonly used tracking protection lists.

Step two: write the first-party script

The local script is simple: /code/check3p.js

All it does is swap out the tracking image source three times.

  • When the script runs, to check that this is a browser with JavaScript on.

  • When the Aloodo tracking script runs, to check if this browser is blocking the script from loading.

  • When the Aloodo script confirms that tracking is possible.

The work is done in the setupAloodo function, which runs after the page loads. First, it sets the src for the tracking pixel to js.png, then sets up two callbacks: one to run after the Aloodo script is loaded, and switch the image to ld.png, and one to run if the script can track the user, and switch the image to td.png.

Step three: check the logs

Now I can use the regular server logs to compare the number of clients that load the original image, and the JavaScript-switched one, to the number that load the two tracking images.

(There are two different tracking callbacks because of the details of how Aloodo has to detect Privacy Badger, among other things. Not all tracking protection works the same.)

I'll run some reports on the logs and post again about the results. (If you want to see your own results in the meantime, you can take a tracking protection test.)