Battery life can be used to identify a user online, even if they try and hide their browsing history and delete cookies, a new study has revealed.
Trackers are intended to find out information about users so they can typically serve them with targeted adverts, but there’s a dark side to them too.
‘Several features of the web…are being used or abused, depending on how one looks at it, by these tracking companies and various entities in the ad tech ecosystem,’ Arvind Narayanan, study co-author and an associate professor of computer science at Princeton said.
‘They’re being used in sneaky ways to track where users are going across the web.’
Computer scientists at the university conducted what they say is the ‘largest and most detailed measurement of online tracking … based on a crawl of the top one million websites,’ using a web privacy measurement tool called OpenWPM.
They measured each site in 15 different ways, including investigating whether they used stateful (cookie-based) and stateless (fingerprinting-based) tracking, and whether they shared tracking data with other sites – a practice known as cookie syncing.
Cookies are text files that are downloaded onto a user’s computer and send relevant information back to a website the next time it’s visited,while fingerprinting techniques pick up on the most discrete of markers to glean information about a user.
The experts discovered two popular web scripts could target people by honing in on the Battery Status API, which is how devices give browsers such as Google Chrome data about a device’s battery life, The Telegraph reported.
This is the first evidence that the method is being used in the real world to track users and is especially troubling as Battery Status API can’t be turned off – unlike cookies.
It even means activity in private browsing modes and virtual private networks can be tracked.
More unconventional methods such as analysing lists of fonts installed by a user and how their browser processes audio data, can also be used.
They experts found that two of the popular sites had 81,000 trackers on them, but most of the tracking was conducted by giants, including Facebook and Google.
Dr Narayanan recommends concerned web users use programs like Ghostery and Disconnect, which block the invisible sites that track a user’s search and browsing history.
They could also install adblockers to reduce the amount they are tracked.
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