Behind Your Business

The U.S. should counter computer-based attacks swiftly and strongly and act to thwart or disable a threat even when the attacker's identity is unknown, the director of the National Security Agency told Congress.

Lt. Gen. Keith Alexander, who is the Obama administration's nominee to take on additional duties as head of the new Cyber Command, also said the U.S. should not be deterred from taking action against countries such as Iran and North Korea just because they might launch cyber attacks.

"Even with the clear understanding that we could experience damage to our infrastructure, we must be prepared to fight through in the worst case scenario," Alexander said in a Senate document obtained by The Associated Press.

Alexander's answers reflect the murky nature of the Internet and the escalating threat of cyber terrorism, which defies borders, operates at the speed of light and can provide deep cover for assailants who can launch disruptive attacks from continents away, using networks of innocent computers.

U.S. computer networks are under constant cyber attacks, by direct assaults by remote sites, by probes by hackers and criminal networks and by espionage from foreign countries. President Barack Obama last year declared that the cyber threat is one of nation's most serious economic and national security challenges.

The three-star Army general laid out his views on Cyber Command and the military's role in protecting computer networks in a 32-page Senate questionnaire. He answered the questions in preparation for a Senate Armed Services Committee hearing Thursday on his nomination to head Cyber Command.

Alexander offered a limited but rare description of offensive U.S. cyber activities, saying the U.S. has "responded to threats, intrusions and even attacks against us in cyberspace," and has conducted exercises and war games.

It's unclear, Alexander added, whether or not those actions have deterred criminals, terrorists or nations.

In cyberspace, he said,...