If the attack could not be repulsed, the new playbook calls for “active defense,” which General Dempsey defined as a “proportional” effort “to go out and disable the particular botnet that was attacking us.” It is notable that, in this situation, the line between active defense and offense might be blurry.

“If it became something more widespread and we needed to do something beyond that, it would require interagency consultation and authorities at a higher level in order to do it,” he said. Although these plans are classified, his statement indicated that the rules for responding in an escalated manner in cyberspace, or with a conventional retaliation, would require decisions by the civilian leadership.

General Dempsey’s speech drew a clear distinction between the nation’s two major efforts in cyberspace. The military’s role is in defending computer networks and, if so ordered by the president, carrying out offensive attacks. That is related to, but separate from, the intelligence community’s efforts to gather intelligence in cyberspace. Several of those highly classified intelligence-gathering programs were exposed via leaks from a former contract worker for the National Security Agency.

Assessing adversaries in cyberspace, General Dempsey said that China, in particular, had chosen a niche in stealing intellectual property. “Their view is that there are no rules of the road in cyber,” General Dempsey noted. He said American and Chinese officials would meet over coming days to discuss ways to “to establish some rules of the road, so that we don’t have these friction points in our relationship.”

The military headquarters responsible for computer-network warfare, the United States Cyber Command, will grow by 4,000 personnel with an additional investment of $23 billion, General Dempsey said. (Cyber Command and the National Security Agency are led by the same officer, Gen. Keith B. Alexander.)

“We are doing all of this not to address run-of-the mill cyberintrusions, but to stop attacks of significant consequence — those that threaten life, limb and the country’s core economic functioning,” General Dempsey said.