Tails, or "The Amnesic Incognito Live System", is a security-focused Debian-based Linux distribution aimed at preserving privacy and anonymity against surveillance.

[11] Laura Poitras, Glenn Greenwald, Bruce Schneier and Barton Gellman have each said that Tails was an important tool they used in their work with National Security Agency whistleblower Edward Snowden.

[20] Tails includes a unique variety of software that handles the encryption of files and internet transmissions, cryptographic signing and hashing, Electrum Bitcoin Wallet, Aircrack-ng and other functions important to security.

It runs in the computer's random access memory (RAM) and does not write to a hard drive or other storage medium.

[24][25] In the same year, Der Spiegel published slides from an internal National Security Agency presentation dating to June 2012, in which the NSA deemed Tails on its own as a "major threat" to its mission and in conjunction with other privacy tools as "catastrophic".

[26][27] In 2017, the FBI used malicious code developed by Facebook, identifying sexual extortionist and Tails user Buster Hernandez through a zero-day vulnerability in the default video player.

Hernandez had eluded authorities for a long time; the FBI and Facebook had searched for him with no success, and resorted to developing the custom hacking tool.