That decision is among several reached in recent months as the administration moves, in the next few weeks, to approve the nation's first rules for how the military can defend, or retaliate, against a major cyberattack. New policies will also govern how the intelligence agencies can carry out searches of faraway computer networks for signs of potential attacks on the United States and, if the president approves, attack adversaries by injecting them with destructive code - even if there is no declared war.