Naturally, there is no advance knowledge of exactly what will be simulated, but unofficial reports suggest one of the major scenarios could involve the chemical industry, said Mike Harmon, who is in charge of the exercise for the CCIP.

New Zealand will have some flexibility when it comes to the scenarios it chooses to run, to reflect our particular vulnerabilities.

'The electricity grid and telecommunications are good things to test in New Zealand,' said Byfield, because management of the two industries is dominated by one company in each sector.

Interruptions to the electricity supply are likely to involve not only the core network but also the digital 'supervisory control and data acquisition' (Scada) network that overlies and controls electricity distribution.

For a long time, Scada been concealed from public view ' Harmon calls it 'security by obscurity' ' but the networks are now connected via the Internet, making them more visible and therefore more vulnerable.