On late Wednesday, The British Guardian daily published classified documents leaked by wanted fugitive Edward Snowden showing that the CIA uses a covert program to monitor internet activity called "XKeyscore".
According to the daily, the NSA tool "collects nearly everything a user does on the internet".
"Training materials for XKeyscore detail how analysts can use it and other systems to mine enormous agency databases by filling in a simple on-screen form giving only a broad justification for the search," the daily reported.
"Under US law, the NSA is required to obtain an individualized Fisa warrant only if the target of their surveillance is a US person, though no such warrant is required for intercepting the communications of Americans with foreign targets," the Guardian noted.
Moreover, one training slide displayed on the Guardian illustrates the digital activity constantly being collected by XKeyscore and the analyst's ability to query the databases at any time.
Analysts can search by name, telephone number, IP address, keywords, the language in which the internet activity was conducted or the type of browser used.
A slide entitled "plug-ins" in a December 2012 document describes the various fields of information that can be searched. It includes "every email address seen in a session by both username and domain", "every phone number seen in a session (eg address book entries or signature block)" and user activity - "the webmail and chat activity to include username, buddylist, machine specific cookies etc".
An analyst can monitor such Facebook chats by entering the Facebook user name and a date range into a simple search screen.
As one slide indicates, the ability to search HTTP activity by keyword permits the analyst access to what the NSA calls "nearly everything a typical user does on the internet".
An example is provided by one XKeyscore document showing an NSA target in Tehran communicating with people in Frankfurt, Amsterdam and New York.
Content remains on the system for only three to five days, while metadata is stored for 30 days. One document explains: "At some sites, the amount of data we receive per day (20+ terabytes) can only be stored for as little as 24 hours."
Source: The Guardian, edited by website team