A tenacious anti-semitic hoax.
Because of it’s influence on Nazi beliefs, it is arguably the most deadly hoax in history.
The text was based on several sources including Maurice Joly’s A Dialogue in Hell: Conversations between Machiavelli and Montesquieu about Power and Right (which had nothing to do with Jews), and the anti-semitic novel Biarritz by “Sir John Retcliffe” (aka: Hermann Goedsche)
The text was first translated into English in Henry Ford’s newspaper The Dearborn Independent.
Derivative marketeers like David Icke continue to profit off the Protocol hoax to this day, making them similar to the bloodthirsty propagandist characters describe in the hoax itself.
References
http://skepdic.com/protocols.html