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 ...