Cyberattack as an act of war
In 2011, The White House published an "International Strategy for Cyberspace" that reserved the right to use military force in response to a cyberattack:
When warranted, the United States will respond to hostile acts in cyberspace as we would to any other threat to our country. We reserve the right to use all necessary means — diplomatic, informational, military, and economic — as appropriate and consistent with applicable international law, in order to defend our Nation, our allies, our partners, and our interests. In so doing, we will exhaust all options before military force whenever we can; will carefully weigh the costs and risks of action against the costs of inaction; and will act in a way that reflects our values and strengthens our legitimacy, seeking broad international support whenever possible.
International Strategy for Cyberspace, The White House, 2011
In 2013, the Defense Science Board, an independent advisory committee to the U.S. Secretary of Defense, went further, stating that "The cyber threat is serious, with potential consequences similar in some ways to the nuclear threat of the Cold War," and recommending, in response to the "most extreme case" (described as a "catastrophic full spectrum cyber attack"), that "Nuclear weapons would remain the ultimate response and anchor the deterrence ladder." In a full-scale attack, the report warns of the following scenario:
Should the United States find itself in a full-scale conflict with a peer adversary, attacks would be expected to include denial of service, data corruption, supply chain corruption, traitorous insiders, kinetic and related non-kinetic attacks at all altitudes from underwater to space. U.S. guns, missiles, and bombs may not fire, or may be directed against our own troops. Resupply, including food, water, ammunition, and fuel may not arrive when or where needed. Military Commanders may rapidly lose trust in the information and ability to control U.S. systems and forces. Once lost, that trust is very difficult to regain.
The impact of a destructive cyber attack on the civilian population would be even greater with no electricity, money, communications, TV, radio, or fuel (electrically pumped). In a short time, food and medicine distribution systems would be ineffective; transportation would fail or become so chaotic as to be useless. Law enforcement, medical staff, and emergency personnel capabilities could be expected to be barely functional in the short term and dysfunctional over sustained periods. If the attack's effects were reversible, damage could be limited to an impact equivalent to a power outage lasting a few days. If an attack’s effects cause physical damage to control systems, pumps, engines, generators, controllers, etc., the unavailability of parts and manufacturing capacity could mean months to years are required to rebuild and reestablish basic infrastructure operation.
Resilient Military Systems and the Advanced Cyber Threat, Defense Science Board, 2013
Cyberwarfare in the United States - Wikipedia, the free encyclopedia