Security experts have identified a new previously unknown mechanism to keep track of a user. It would be implemented on 5% of the most popular websites.

AddThisThe best known method to present identify a user, and to return to targeted advertising, typically is the traditional cookie. You can block these small files with specific extensions. However, researchers from the Universities of Leuven and Ku Princeton claim to have discovered another method remained in the shadows until now. system in question is mainly developed by AddThis, offering different share buttons.

It would be to send an instruction to the user’s browser so that it draws a small hidden image. Since these drawings would present some variations from one machine to another, so they are a digital fingerprint that can be translated as a unique identifier. It will then be possible to isolate a computer and know the history of visited websites on a browser. At present it is not yet possible to block this statement, which is present in 5% of the 100 000 Web sites most popular.

These are indeed in use widgets sharing offered by AddThis. A list of sites affected by this tracker is available on this page . Among the sites affected French, we rely Weather France, LeGorafi, Telerama, MetroNews, The, several academic institutions or various sites in French cities (Lyon Montpellier). Asked by the magazine ProPublica , Rich Harris, CEO of AddThis, said the company is testing the digital footprint since the beginning of the year.

The company seeks indeed an alternative to traditional cookie. Mr. Harris said that the mechanism does not violate the laws. AddThis does not use the data collected for advertising purposes but for internal use. The company provides a mechanism to opt out via the installation … a cookie.