GCHQ is leading a pioneering scheme to combat cyber crime after it was revealed the offence was costing the country £27 billion a year.
GCHQ will guide some of the country's top business minds against internet warfare.
It's free Cyber Security for Business programme will help private companies heighten their responses to the 21st-century threat.
It comes amid concern about the growing threat of cyber warfare to the British economy. A report by the Commons Intelligence and Security Committee concluded the UK's defences remained inadequate despite a £650 million cyber security programme.
Jonathan Evans, head of MI5, has described an "astonishing" level of state and criminal cyber attacks.
One London business lost £800 million on a single occasion, while in Gloucestershire, self-styled lord Hugh James Rodley, of Twyning, was jailed for eight years after attempting to hack into bank accounts and siphon off £229 million in 2004. Then earlier this year, Jay Moore, of Cromhall, near Wotton-under-Edge, was jailed for three years for cyber fraud worth more than £26.9 million.
He set up the Freshshop website to sell stolen financial data in bulk.
A spokesman for GCHQ said: "Currently, too few company chief executives and chairs take a direct interest in protecting their businesses from cyber threats.
"So now, for the first time, the Government and intelligence agencies are directly targeting the most senior levels in the UK's largest companies and providing them with advice on how to safeguard their most valuable assets, such as personal data, online services and intellectual property."
The programme, in association with the Department for Business, Innovation and Skills, was launched yesterday.
Business Secretary Vince Cable said: "Cyber security threats pose a real and significant risk to UK business by targeting valuable assets such as data and intellectual property.
"By properly protecting themselves against attacks companies are protecting their bottom line."
The new guidance was produced by the Information Security arm of GCHQ, which is based at the iconic doughnut in Benhall.