We always knew it, but necessarily how,
Here is an interesting article on theguardian about Xkeyscore, a software used by the NSA.
Summary:
XKeyscore: NSA tool collects ‘nearly everything a user does on the internet’
XKeyscore gives ‘widest-reaching’ collection of online data
NSA analysts require no prior authorization for searches
Sweeps up emails, social media activity and browsing history
