Washington (CNN) -- The top general responsible for protecting the U.S. military from cyber attack said Thursday that he doesn't have the authority to defend all the country's computers and infrastructure, such as power grids and telecommunications systems.
"It is not my mission to defend -- today -- the entire nation," Gen. Keith Alexander told the House Armed Services Committee. He simultaneously runs both the newly created Cyber Command as well as the National Security Agency.
"Our mission in Cyber Command is to defend the Defense Department networks," Alexander said.
He said the White House and Departments of Defense and Homeland Security were consulting about how to work together in the event of a national cyber emergency
"Those are the steps we are going through, under the leadership of the White House right now," Alexander said.
He told the committee that cyber attacks against the United States are relentless: Department of Defense computer networks are probed 250,000 times an hour. And he said that an attack on critical infrastructure would require first response not from the Pentagon but from private industry.
"If an attack were to go to the power grids right now, the defense of that would rely heavily on commercial industry to protect it," he said
Alexander was confirmed as the first cyber commander of the Defense Department in May, and his team of 1,100 military personnel and computer experts isn't expected to get fully up to speed until next month.
He predicted that his command will be forced to grow in the future and he said his team would need a new dynamic, active approach to cope with future threats.
"This is a work in progress, what we are doing at Cyber Command," he said. "It is going to have to grow."
Alexander may be the point man for some of the most sophisticated electronic wizardry in the U.S. arsenal, but he took a low-tech approach when he briefed Congress. He relied on papers rather than laptops. Only a loose-leaf binder and a notepad, nameplate and a water bottle were on the witness desk in front of him.
There was no sign of the Apple iPad the general described in his written testimony to the committee.
"I recently bought an iPad. Its capability surpasses that of even NASA computers of 20 years ago," Alexander said.
He used the iPad, and its millions of lines of computer code and its variety of applications, as an example of modern complexities.
"You begin to grasp the complexity of our new world and the ways in which our economy and society have shifted to an information culture," Alexander wrote in his advance testimony, "where wealth is less and less rooted in the physical ability to manipulate objects than it is in the knowledge of how those objects work together."