William Lynn, the U.S. deputy defense secretary, said technological infrastructure links the United States and Canada so strongly that a cyberattack on would be felt almost instantly by the other, the Pentagon said.
"But both geography and the closeness of the alliance with Canada, makes Canada a particularly important partner as we tackle these threats," he said.
In terms of conventional deterrence, the defense secretary said, attacks by militant group or rogue states area easy to trace.
"Missiles come with a return address," he said. "You know who launched it."
Lynn said that in terms of cyber-deterrence, however, the status quo may not be the best defense, especially with moderately resourced groups.
"Deterrence works if the other side has something to lose," he said. "These groups may not have anything."
NATO, he added, included cybersecurity as a vital component of the strategic posture for the alliance.