It is unclear how carefully the administration has weighed the various risks involved if the plan is acted on in classified operations. Adversaries like Russia, China and North Korea, all nuclear-armed states, have been behind major cyberattacks, and the United States has struggled with the question of how to avoid an unforeseen escalation as it wields its growing cyberarsenal.

Another complicating factor is that taking action against an adversary often requires surreptitiously operating in the networks of an ally, like Germany — a problem that often gave the Obama administration pause.

The new strategy envisions constant, disruptive “short of war” activities in foreign computer networks. It is born, officials said, of more than a decade of counterterrorism operations, where the United States learned that the best way to take on Al Qaeda or the Islamic State was by destroying the militants inside their bases or their living rooms.