'US infrastructure highly vulnerable to cyber attack'

NSA chief makes disclosure during testimony to Congress

US critical infrastructure - which ranges from telecommunications to water to energy supplies - is not well prepared to handle a destructive cyber attack, the top US general in charge of cybersecurity has said.

National Security Agency (NSA) chief General Keith Alexander, making his first public appearance since revelations surfaced last week about US telephone and internet surveillance efforts, made the comments in a statement prepared for testimony before Congress on Wednesday.

"On a scale of one to 10, with 10 being strongly defended, our critical infrastructure's preparedness to withstand a destructive cyber attack is about a three based on my experience," Alexander, also in charge of the US military's Cyber Command, wrote in the statement prepared for the Senate Appropriations Committee for a hearing on cybersecurity.

Alexander said the US has been and continues to be a target of cyberattacks by foreign nations.

About 90 per cent of the nation's critical infrastructure is owned by the private sector, and therefore is not under the control of the US government or military.

While he made no mention of the leaks about NSA surveillance programmes, Alexander said it was vital to have a strong US Defense Department role in cyberspace in light of what he called real and growing threats.