"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." See the article:
“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.”
See the article: NSA uses Google cookies to pinpoint targets for hacking (Washington Post, link)
Also see: Slide from an internal NSA presentation (pdf)