Edward Snowden, The National Security Agency has a secret program that allows it to see just about everything a person does on the Internet. XKeyscore collects more than 20 terabytes of information daily, including emails, chats, social media interactions, and even browsing histories all in real-time. At least 41 billion records were collected and stored in a single 30-day period in 2012, according to the report. NSA documents show that as of 2008, the X-Keyscore platform was used to nab 300 alleged terrorists around the world.
Source: https://thehackernews.com/2013/07/nsas-xkeyscore-program-could-read.html