Invisible Pixels Are Dead, Long Live Invisible Pixels!

TL;DR

Despite advancements in privacy tools, classical 1x1 web beacons remain widely used for third-party tracking, and limited information can effectively identify them, highlighting ongoing privacy challenges.

Contribution

This paper demonstrates that traditional 1x1 web beacons are still prevalent and can be accurately classified, despite modern tracking techniques and ad-blockers.

Findings

Classical 1x1 images are still commonly used for tracking.

Limited information can classify these images with 95.6% accuracy.

Ad-blockers are often ineffective against these traditional beacons.

Abstract

Privacy has deteriorated in the world wide web ever since the 1990s. The tracking of browsing habits by different third-parties has been at the center of this deterioration. Web cookies and so-called web beacons have been the classical ways to implement third-party tracking. Due to the introduction of more sophisticated technical tracking solutions and other fundamental transformations, the use of classical image-based web beacons might be expected to have lost their appeal. According to a sample of over thirty thousand images collected from popular websites, this paper shows that such an assumption is a fallacy: classical 1 x 1 images are still commonly used for third-party tracking in the contemporary world wide web. While it seems that ad-blockers are unable to fully block these classical image-based tracking beacons, the paper further demonstrates that even limited information can be used to accurately classify the third-party 1 x 1 images from other images. An average classification accuracy of 0.956 is reached in the empirical experiment. With these results the paper contributes to the ongoing attempts to better understand the lack of privacy in the world wide web, and the means by which the situation might be eventually improved.