The National Security Agency is secretly piggybacking on the tools that enable Internet advertisers to track consumers, using “cookies” and location data to pinpoint targets for government hacking and to bolster surveillance. This cookie allows NSA to single out an individual’s communications among the sea of Internet data in order to send out software that can hack that person’s computer.
How the NSA obtains Google PREF cookies or whether the company cooperates in these programs is not known, but other documents reviewed by the Post indicate that cookie information is among the data NSA can obtain with a Foreign Intelligence Surveillance Act order. If the NSA gets the data that way, the companies know and are legally compelled to assist. Link