Everybody Spies in Cyberspace. The U.S. Must Plan Accordingly.

The recently revealed SolarWinds hack unfolded like a scene from a horror movie: Victims frantically barricaded the doors, only to discover that the enemy had been hiding inside the house the whole time. For months, intruders have been roaming wild inside the nation’s government networks, nearly all of the Fortune 500, and thousands of other companies and organizations. The breach—believed to be the work of an elite Russian spy agency—penetrated the Pentagon, nuclear labs, the State Department, the Department of Homeland Security (DHS), and other offices that used network-monitoring software made by Texas-based SolarWinds. America’s intelligence agencies and cyberwarriors never detected a problem. Instead, the breach was caught by the cybersecurity firm FireEye, which itself was a victim.

The full extent of the damage won’t be known for months, perhaps years. What’s clear is that it’s massive—“a grave risk to the federal government …