While we surf on the Internet we leave an impressive amount of traces that could be used to track our profile and also reveal our identity even we are visiting resources in the darknet.
The way a user moves writes a blog post or moves a mouse could allow to track him.
“While preventing users IP address to be disclosed is a key aspect for protecting their privacy, a lot of other things need to be taken into consideration. Tor browser is preconfigured to prevent a lot of possible attacks on user privacy, not only the communications layer provided by tor itself.” wrote Jose Carlos Norte.
“One common problem that tor browser tries to address is user fingerprinting. If a website is able to generate a unique fingerprint that identifies each user that enters the page, then it is possible to track the activity of this user in time, for example, correlate visits of the user during an entire year, knowing that its the same user. Or even worse, it could be possible to identify the user if the fingerprint is the same in tor browser and in the normal browser used to browse internet. It is very important for the tor browser to prevent any attempt on fingerprinting the user.”
The expert created a quick and dirty PoC called UberCookie to demonstrate that is possible to fingerprint a user in a controlled environment.
Norte explained that the most interesting fingerprinting vector he discovered on Tor Browser is getClientRects that allows to get the exact pixel position and size of the box of a given DOM element.
The results of the getClientRects call depend on multiple factors, including the resolution and the font configuration that can compose the fingerprinting vector.
Lorenzo Bicchierai from MotherBoard tried to contact members of the Tor Project and is still waiting for a reply.
The popular cyber security expert Mikko Hypponen published a Tweet that define “clever” the technique.
Clever! Fingerprinting a website user based on his mouse wheel moves, as reported by your browser. Has a demo, too. https://t.co/0MDkmpfxc5
— Mikko Hypponen (@mikko) 8 Marzo 2016
(Security Affairs – Tor network, fingerprint)