The US Department of Homeland Security (DHS) has completed its Cyber Storm government-led IT security exercise.

Cyber Storm aimed to examine response, coordination and recovery mechanisms to a simulated "cyber-event" within international, federal, state and local governments in conjunction with the private sector.

The DHS reported that 115 public, private and international agencies, organisations and companies were involved in the planning and implementation of Cyber Storm.

"Cyber-security is critical to protecting our nation's infrastructure because information systems connect so many aspects of our economy and society," said George Foresman, Under Secretary for Preparedness at the DHS.

"Preparedness against a cyber attack requires partnership and coordination between all levels of government and the private sector. Cyber Storm provides an excellent opportunity to enhance our nation's cyber preparedness and better manage risk."

The exercise simulated a sophisticated cyber attack through a series of scenarios directed against critical infrastructures.

One of the scenarios simulated an incident where a utility company's computer system was breached, causing numerous disruptions to the power grid.

According to Foresman, the intention of this scenario is to highlight the " interconnectedness" of cyber security with the physical infrastructure and to exercise coordination and communication between the public and private sectors.

The DHS stressed that the exercise was a simulated event and that "there were no real world effects on, tampering with, or damage to any critical infrastructure".

The government department added that, while the exercise was based on a hypothetical situation, it was not intended as a forecast of future terrorist threats.

Cyber Storm participants included members of the public sector (federal and state agencies), the private sector (IT, telecoms, energy and transportation firms) and international government partners.