"Princeton's Arvind Narayanan and Steven Englehardt studied how all the things we do not see as users are valuable to someone on our digital trail, as our presence may be authenticated and tracked through such minutia as personalized browser settings or even our laptops' battery levels.
Fingerprinting "allows a tracker to put an identifier on your entire history of online activity," Narayanan, assistant professor of computer science, tells NPR's Robert Siegel. "They've been collecting those histories, that's not new — that's a given. But what the technological sophistication is for, is for linking all of your online breadcrumbs together, even if you're not necessarily putting your real name or email address into all your online interactions.""