The CIA has revealed that cyber terrorists have left several cities outside the USA without power by hacking into power grids, demanding money in return for switching the lights back on. It would appear that the nightmare scenario envisaged in films like Die Hard 4 has now become a reality.

In a statement given to a major US security conference, CIA official Tom Donahue revealed that America's security agency knew of a number of successful attacks on power grids outside the US that had resulted in blackouts and demands for money.

Lights go out, walls come tumblin' down

Donahue revealed how in at least one case the attacks had "caused a power outage affecting multiple cities". The CIA has refused to name the cities or countries affected by the attacks, but confirmed that all the attacks had taken place through the internet.

According to the CIA statement, the hackers' success in compromising infrastructure security systems may have been aided by insider knowledge, although they have no way of proving this. Although blackmail was certainly one factor no other motives were presented: "We do not know who executed these attacks or why, but all involved intrusions through the internet," the statement read.

The statement has led to renewed calls for more attention to be focused on the security of Supervisory Control and Data Acquisition (SCADA) systems that are used to manage many civic utilities and infrastructure. The vulnerability of SCADA systems has concerned IT security specialists for many years.

Although numerous checks and balances aimed at preventing wholesale meltdown are incorporated into most SCADA systems, the CIA's evidence suggests that there are still ways to circumnavigate even the tightest security.