Digital Fortress is a techno-thriller novel written by American author Dan Brown and published in 1998 by St. Martin's Press.

The book explores the theme of government surveillance of electronically stored information on the private lives of citizens, and the possible civil liberties and ethical implications of using such technology.

When the United States National Security Agency's (NSA) code-breaking supercomputer TRANSLTR encounters a revolutionary new code, Digital Fortress, that it cannot break, Commander Trevor Strathmore calls in head cryptographer Susan Fletcher to crack it.

Strathmore tells Fletcher that Tankado has in fact died in Seville at the age of 32, of what appears to be a heart attack.

Strathmore asks Fletcher's fiancé David Becker to travel to Seville and recover a ring that Tankado was wearing when he died.

Unbeknown to Becker, a mysterious figure, named Hulohot, follows him, and murders each person he questions in the search for the ring.

Becker manages to track down the ring, but ends up pursued by Hulohot in a long cat-and-mouse chase across Seville.

The two eventually face off in a cathedral, where Becker finally kills Hulohot by tripping him down a spiral staircase, causing him to break his neck.

However, Strathmore was unaware that Digital Fortress is actually a computer worm that, once unlocked would "eat away" all the NSA databank's security and allow "any third-grader with a modem" to look at government secrets.

Imagine Entertainment announced in 2014 that it is set to produce a television series based on Digital Fortress, to be written by Josh Goldin and Rachel Abramowitz.