NSA chief warns of cyber attack danger from nation states

The deputy director of the US National Security Agency (NSA), Richard Ledgett, has warned of the increasing danger of destructive cyber attacks by states.

"If you are connected to the internet, you are vulnerable to determined nation-state attackers," he told security correspondent Gordon Corera.

He also said agency targets, numbered in "the high hundreds", had discussed leaks by contractor Edward Snowden, with some changing their behaviour as a result.