Back in December, documents revealed the NSA had been using Googles ad-tracking cookies to follow browsers across the web, effectively coopting ad networks into surveillance networks. A new paper from computer scientists at Princeton breaks down exactly how easy it is, even without the resources and access of the NSA. The researchers were able to reconstuct as much as 90% of a users web activity just from monitoring traffic to ad-trackers like Googles DoubleClick. Tor was the only tool that escaped the researchers dragnet