Browser privacy settings on high? Ad blocker engaged? A difficult to evade web tracking technique could still follow your internet activity for months.
Tracking people on the internet is normally done using cookies 鈥� tiny files that websites place on your computer. These are used for security purposes, for instance detecting suspicious online banking logins, and also by advertisers to target people with ads based on their browsing habits.
But as many people have started to use online privacy tools such as ad blockers, tracking using cookies has聽become increasingly ineffective. Iskander Sanchez-Rola at the University of Deusto in Spain and colleagues developed a tracking tool that relies on tiny variations in a device鈥檚 hardware instead.
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The tool works by measuring subtle differences in quartz crystals in computer clocks, which affect how quickly websites are processed. These differences appear consistently and so act as a digital fingerprint for a device.
When 300 volunteers made a one-off visit to a website running the tool, it could uniquely fingerprint around half of them. When combined with other techniques that measure how graphics are rendered on screen it rose to 80 per cent.
鈥淩esults indicate that our technique is far more reliable and practical than any existing fingerprinting technique,鈥� says Sanchez-Rola. The team presented the tracking tool at the ACM in Toronto last month.
Most previous attempts to develop trackers have relied on measuring software attributes, like a device鈥檚 screen resolution, browser version or supported fonts. But many of these attributes shift frequently with updates and settings changes, meaning the fingerprints typically last just days. In comparison, Sanchez-Rola鈥檚 tool can create fingerprints that last several months.
The accuracy and long-term tracking are significant contributions and real-world trackers are likely to adopt the technique, says Yinzhi Cao at Johns Hopkins University.
鈥淚t is unfortunately the case that modern computers are too diverse, and there are too many ways that diversity can be noticed and used by trackers,鈥� says Peter Eckersley at the Electronic Frontier Foundation. Privacy tools must keep improving to stay ahead of subtle fingerprinting techniques, he adds.
