A former CIA chief says other governments could launch crippling computer attacks on the U.S.

A former Director of Counterintelligence for the CIA - Barry Royden - believes that cyber terrorism is the next big threat to America.

Royden, who spent 40 years in the CIA - 35 years as an operative and 5 years as head of counterintelligence - knows what he's talking about. Though he's been retired for more than a decade, he isn't blind to what he believes is a new type of threat that has emerged in an increasingly connected world:

"The trouble is, it's extremely difficult, in fact, it's impossible - everyone is connected to everyone, and as long as you're connected you're vulnerable. And there are firewalls, but every firewall is potentially defeatable, so it's a nightmare in my mind. You have to think that other governments have the capability to bring down the main computer systems in this country, power grids, hospitals, or banking systems - things that could cause great economic upheaval and paralyze the country."

He adds:

"Now, if they were to do it to us and we were to do it to them, it would almost be like a nuclear standoff. They could do it but if they did it what would the cost be? Because they know we have the same capabilities and that we presumably attack their computer systems the same way and we could destroy their economy. So you hope that no one is going to do that but you're vulnerable. These days, I think the cyber world is the big threat."