Edward Snowden sign held up by protesters
Edward Snowden has advised that citizens secure their data using full disc encryption, i.e. TailsReuters

Whistle-blower Edward Snowden has been using a super-secure computer operating system called Tails that comes with encryption and privacy tools to make the user completely anonymous on the internet.

During his live video interview with SXSW last month, Edward Snowden mentioned that one way citizens could secure their data to prevent being spied on by their ISPs or government agencies was to use "full disc encryption".

Well, now we know that means. Meet Tails (which stands for The Amnesic Incognito Live System), a super-secure free operating system that runs on open-source Linux software.

All you have to do is download it from the official website, install it either on a DVD, a USB memory stick or an SD card, access the software on a computer, and immediately you're in a completely separate operating system that makes you anonymous on the internet.

Tails won the Endpoint Security Award, part of the 2014 Access Innovation Prize last month for improving secure communications in high-risk environments.

How does Tails work?

In order to keep the user anonymous, all web traffic is routed through Tor (which stands for The Onion Router), a network of thousands of servers across the globe run by volunteers.

Tails is so small it can fit easily onto a USB memory stick
Tails is so small it can fit easily onto a USB memory stickCTR, Free Images

It is next to impossible to track data sent through the Dark Web and websites in this part of the internet cannot be found through search engines like Google, Yahoo or Bing.

Another encryption tool called GPG email encryption, which offers public key encryption to keep your message encrypted until it gets to the other party, is also included.

"Using Tails on a computer doesn't alter or depend on the operating system installed on it. So you can use it in the same way on your computer, a friend's or one at your local library. After shutting down Tails, the computer can start again on its usual operating system," the Tails website explains.

Tails leaves no trace on any computer you use it on, as it doesn't store data locally. This means that malware cannot affect it and someone analysing the computer after you've used it won't be able to find out what you were doing.

It is not known who created Tails in 2009, but it has been mostly funded by the Tor Project and is maintained by an online community of software developers on numerous Git repositories, where lots of people can work on source code at once.

Maintaining online privacy

Journalists Glenn Greenwald of The Guardian and Barton Gellman of The Washington Post, together with American documentary filmmaker Laura Poitras, all used Tails in order to communicate securely with Snowdon.

"Privacy and encryption work, but it's too easy to make a mistake that exposes you," said Gellman in a Press Freedom Foundation blog recently.

"Tails puts the essential tools in one place, with a design that makes it hard to screw them up. I could not have talked to Edward Snowden without this kind of protection. I wish I'd had it years ago."

Barton Gellman of the Washington Post
Barton Gellman of the Washington Post, who has won awards for his coverage of the NSA revelationsGetty Images

The important thing to know is that while using Tails, you'll have access to some open-source free productivity applications like OpenOffice for desktop publishing, GIMP for image editing and Audacity for playing and editing music, but Tails is really designed to be used only for crucial activities that need to remain anonymous.

Otherwise, using other services on the web that require you to login could completely blow your cover.

At the moment, the community running Tails is so short of funds that none of the volunteers can afford to work full-time on maintaining the software.

Tails is also working on a mobile operating system called Tomy that would enable users to run a completely secure OS on their phone that boots from a microSD card.

You can donate to support open-source encryption tools like Tails on the Press Freedom Foundation website here.