It is soo easy to forget about just how much identifying metadata you leave on the internet just by reading stuff.
You know the cookie banners you see? Those that claim to let you opt out from being tracked by advertisers?
Yeah, those are just the overt tracking mechanism, tracking pixels are far far more insidious.
Lets backtrack a bit, back when Facebook started getting big, companies started embedded Like buttons on their webpages, cool right? You could just click the Like button and it would help you post a link to your Facebook feed to the page you were visiting.
Seems fine, right? What’s the issue?
It would be fine if the image of the Like button was stored on the local web server hosting the rest of the site.
But it isn’t.
It is stored on Facebook’s servers, it is stored in a way that every single Like button has their own ID, so every time you load up your favourite website about abandoned radiation experiment sites it makes your browser send a request to Facebook’s servers as well and depending on how the request is sent they can at minimum log that your IP address loaded the Like button with the ID number X, the ID number X is tied to the specific webpage you visited.
Then you go and do some research on impotense and how to cure it, the pages you read all have Like buttons as above, but with their own ID numbers, Facebook now knows at a minimum that you are a man who is interested in science, technology, society and modern history, you may also suffer from impotense.
Well, you keep browsing the web and read local news, well the Like button is also there, and with the ID number Facebook can add an area of interest to your profile.
It keeps going like this, but with one huge important change, people are starting getting warey of the Like buttons and Facebook in general, so they simply remove the button, while introducing the tracking pixel, a 1px*1px transparent picture, it works like how the Like button loads, and keeps generating data for Facebook.
Facebook is not alone in this, I just used them as an example.
You can read more here:
https://en.wikipedia.org/wiki/Spy_pixel
This is also not even getting into browser fingerprinting.
I have not read that book, but seeing as the right is on the rise also here in Europe, it might be worth checking it out.