Eight weeks later, General Nakasone and other American officials responsible for cybersecurity are now consumed by what they missed for at least nine months: a hacking, now believed to have affected upward of 250 federal agencies and businesses, that Russia aimed not at the election system but at the rest of the United States government and many large American corporations.

Three weeks after the intrusion came to light, American officials are still trying to understand whether what the Russians pulled off was simply an espionage operation inside the systems of the American bureaucracy or something more sinister, inserting “backdoor” access into government agencies, major corporations, the electric grid and laboratories developing and transporting new generations of nuclear weapons…

Those questions have taken on particular urgency given that the breach was not detected by any of the government agencies that share responsibility for cyberdefense — the military’s Cyber Command and the National Security Agency, both of which are run by General Nakasone, and the Department of Homeland Security — but by a private cybersecurity company, FireEye.

“This is looking much, much worse than I first feared,” said Senator Mark Warner, Democrat of Virginia and the ranking member of the Senate Intelligence Committee. “The size of it keeps expanding. It’s clear the United States government missed it.”