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From here [1]: For new users who install and download Firefox for the first time, Enhanced Tracking Protection will automatically be set on by default as part

From here [1]: For new users who install and download Firefox for the first time, Enhanced Tracking Protection will automatically be set on by default as part of the ‘Standard’ setting in the browser and will block known “third-party tracking cookies” according to the Disconnect list. We talk more about tracking cookies here. Enhanced Tracking Protection will be practically invisible to you and you’ll only notice that it’s operating when you visit a site and see a shield icon in the address bar next to the URL address and the small “i” icon. When you see the shield icon, you should feel safe that Firefox is blocking thousands of companies from your online activity. A better source is probably the disconnect site [2]: > Tracking is the collection of data regarding a particular user's activity across multiple websites or applications that aren’t owned by the data collector, and the retention, use or sharing of that data. > Our definition focuses on collection AND retention. So, for example, the definition wouldn’t apply to sites that log an IP address, but don’t save that information in a database. The definition also focuses on particular users, so data that is immediately aggregated doesn’t apply. And the collection is across context, so it doesn’t apply in cases when there is solely a first-party relationship with the user, for example the site only collects and retains information on site visitors. [1]: https://blog.mozilla.org/blog/2019/06/04/firefox-now-available-with-enhanced-tracking-protection-by-default/ https://blog.mozilla.org/blog/2019/06/04/firefox-now-availab... [2]: https://disconnect.me/trackerprotection https://disconnect.me/trackerprotection

cmrdporcupine 7y ago
This isn't really explaining the "how" to me though. The way I remember it is, as the page host I have a cookie on you. Then I drop in a 1-pixel image to a third party, and in the query string to it I write in a hashed form of the cookie I have for you. That HTTP request then itself can go through the cookie process, but for the third party. They then check their DB for both their own issued cookie and the value you passed in, and are then able to perform some asynchronous (batch or otherwise) match to associate the two IDs. From then on, an ad etc. can be targeted based on that info.
- greenyoda 7y ago
  Yeah, it doesn't seem that merely blocking third party cookies can address a scenario like this, where the main site colludes with the third party tracking site. To avoid this, it still seems like the best approach is to use an ad blocker add-on like uBlock Origin, which will block any content from known tracking domains from being loaded. That should get rid of the third party image. There's also uMatrix (from the maker of uBlock Origin), which can selectively block images, scripts, etc. from third party sites.

cmrdporcupine 7y ago

This isn't really explaining the "how" to me though. The way I remember it is, as the page host I have a cookie on you. Then I drop in a 1-pixel image to a third party, and in the query string to it I write in a hashed form of the cookie I have for you. That HTTP request then itself can go through the cookie process, but for the third party. They then check their DB for both their own issued cookie and the value you passed in, and are then able to perform some asynchronous (batch or otherwise) match to associate the two IDs. From then on, an ad etc. can be targeted based on that info.

greenyoda 7y ago
Yeah, it doesn't seem that merely blocking third party cookies can address a scenario like this, where the main site colludes with the third party tracking site. To avoid this, it still seems like the best approach is to use an ad blocker add-on like uBlock Origin, which will block any content from known tracking domains from being loaded. That should get rid of the third party image. There's also uMatrix (from the maker of uBlock Origin), which can selectively block images, scripts, etc. from third party sites.