Even if you use private browsing, block ads, or hide your tracks, some websites still monitor every online movement you make, using a new web-tracking technique called Audio Fingerprinting.
This new Fingerprinting technique can be used by companies for targeted advertising distribution, as well as by law enforcement authorities to expose VPNs or anonymous users, without even needing to decrypt traffic.
Most of you have encountered the technique, but in another harmless form: it is used by the Shazam application.
Researchers at Princeton University conducted a massive study and discovered that Google, through the many domains it uses in its services, tracks users from 80% of the total of the top 1 million domains, using several tracking methods and techniques.
Among them, the most recent detection technology discovered by the researchers is one that relies on capturing “fingerprints” of a machine's sound via the AudioContext API. That's why: Audio Fingerprinting.
“All top domains, as well as 12 of the first 20, are owned by Google”, note the researchers.
The AudioContext API does not collect sounds that were played or recorded by a device, but it collects the acoustic signatures of each device which are then used to create unique combinations of the browser with the device.
The method does not have anything to do with the device's microphone, as it relies on the way a signal is processed.
A third‑party tracker now uses the AudioContext API to send low‑frequency sounds to the user's computer and then measures how long the computer needs to process the data, creating a unique fingerprint based on the capabilities of the computer's hardware and software.
The top websites that use Audio Fingerprinting to track you secretly:
The researchers, Associate Professor Arvind Narayanan and graduate student Steven Englehardt, created a page for a live demonstration of the technique. So, if you want to check the audio fingerprints left by your device you can do it from the test page.
https://audiofingerprint.openwpm.com/
The Audio Fingerprinting technique has not been widely adopted but appears to use a range of different approaches that together monitor “silently” those who browse the Internet.
To conduct the measurements and monitor the trackers, the researchers used a custom open-source software called OpenWPM, which loads websites in Chrome, Firefox, and Internet Explorer, and tracks data collection on every page that loads.
