The National Security Agency (NSA) maintains a secret surveillance program called X-Keyscore that, according to new revelations by The Guardian, “allows analysts to search with no prior authorization through vast databases containing e-mails, online chats, and the browsing histories of millions of individuals, according to documents provided by whistleblower Edward Snowden.”

On Wednesday morning, the British newspaper published a series of training slides showing that NSA analysts have the ability to search vast databases of information, including "nearly everything a typical user does on the Internet.” One of the slides calls X-Keyscore the NSA’s "widest-reaching" system for digital surveillance.

In the very first video interview with The Guardian from nearly two months ago, Snowden claimed that just by sitting at his desk, he could "wiretap anyone, from you or your accountant to a federal judge or even the president if I had a personal e-mail.” Government officials pounced on this claim, denying it specifically—Rep. Mike Rogers (R-MI), the head of the House intelligence committee, said that Snowden was “lying.”

But The Guardian now reports:

The purpose of XKeyscore is to allow analysts to search the metadata as well as the content of emails and other internet activity, such as browser history, even when there is no known email account (a "selector" in NSA parlance) associated with the individual being targeted. Analysts can also search by name, telephone number, IP address, keywords, the language in which the Internet activity was conducted or the type of browser used. One document notes that this is because "strong selection [search by email address] itself gives us only a very limited capability" because "a large amount of time spent on the Web is performing actions that are anonymous."

It appears, based on these newly published slides, that the NSA is capturing vast swaths of unencrypted HTTP traffic at sites that span the entire world. However, due to storage limitations, it seems that it can only keep that data for relatively short periods of time. As Ars has described before, it would be nearly impossible for the NSA to store things for an extended period of time—one slide says that for a single 30-day period in 2012, the data included “at least 41 billion total records.”

This is confirmed by The Guardian:

The XKeyscore system is continuously collecting so much Internet data that it can be stored only for short periods of time. 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."

The NSA also appears to have the ability to log, search, and track individual IP addresses as they connect with a variety of sites around the Internet. One slide details an Tehran-based IP address and shows it connects to Mail.com in New York, then to a Facebook server in Frankfurt, and then to BBC.co.uk in London.

Encryption methods such as HTTPS, a Virtual Private Network (VPN), or Tor are more resistant (but likely not 100 percent bulletproof) to such surveillance techniques.

In a statement provided to the British newspaper, the NSA said: