Canvas Fingerprinting ⇥ propublica.org

Julia Angwin, reporting for ProPublica:

First documented in a forthcoming paper by researchers at Princeton University and KU Leuven University in Belgium, this type of tracking, called canvas fingerprinting, works by instructing the visitor’s Web browser to draw a hidden image. Because each computer draws the image slightly differently, the images can be used to assign each user’s device a number that uniquely identifies it.

[…]

Rich Harris, chief executive of AddThis, said that the company began testing canvas fingerprinting earlier this year as a possible way to replace “cookies,” the traditional way that users are tracked, via text files installed on their computers.

“We’re looking for a cookie alternative,” Harris said in an interview.

Clever.

And wrong. Consider the two main ways you may attempt to avoid being tracked by advertisers on the internet:

1. using the Do Not Track setting in your browser; and,
2. changing your browser’s cookie settings to block third party cookies.

The first setting is completely optional for advertisers to follow, rendering it effectively meaningless. The second setting does not impact this fingerprinting scheme in any way, which means that this is similar to Google’s workaround for Safari’s default setting to block third party cookies, for which they were fined $17 million.

So how do you opt out of this? Well, cookies are back in style:

He added that the company has only used the data collected from canvas fingerprints for internal research and development. The company won’t use the data for ad targeting or personalization if users install the AddThis opt-out cookie on their computers, he said.

In essence, you’re not opting out of the collection of your data, but instead hoping that AddThis won’t use the data it collects for anything other than internal research. Which is soothing, isn’t it?