Using his "super user" status on internal computer systems, William Culbert threatened to cause mayhem at Associated Newspapers, which publishes the Daily Mail, the Evening Standard and the Metro.
Culbert, a 55-year-old former Daily Mail print technician, told rival publisher Express Newspapers that, for a £600,000 kickback and tickets to leave the country, he would destroy the Associated Newspapers.
Southwark Crown Court heard that had Culbert gone ahead with his revenge he would have caused £13.4m of chaos.
Culbert claimed he would also take-out print centres in the UK, Spain and the US.
However, Paul Rudd, a production editor at the Express who was approached by Culbert last November, went straight to Scotland Yard's Computer Crime Unit to report the intended "industrial sabotage".
Further conversations were covertly recorded, leading to Culbert's arrest on 16 December. Subsequently, Associated Newspapers has stepped up its security.
Culbert admitted two charges of an unauthorised modification of a computer system, and one charge of gaining unauthorised access to a computer system - offences that carry a maximum five-year jail term.
Judge Peter Fingret sentenced the defendant to 18 months imprisonment.