If cyberarms-control is to America’s advantage, it would be wise to shape such accords while it still has the upper hand in cyberspace. General Keith Alexander, the four-star general who heads Cyber Command, is therefore right to welcome Russia’s longstanding calls for a treaty as a “starting point for international debate”. That said, a START-style treaty may prove impossible to negotiate. Nuclear warheads can be counted and missiles tracked. Cyber-weapons are more like biological agents; they can be made just about anywhere.