Experts say it's going to take months to kick elite hackers, widely believed to be Russian, out of U.S. government networks.
The hackers have been quietly rifling through those networks for months in Washington's worst cyberespionage failure on record.
Experts say there simply are not enough threat-hunting teams to identify all the government and private-sector systems that may have been hacked.
FireEye is the cybersecurity company that discovered the worst-ever intrusion into U.S. agencies and was among the victims.
It has already tallied dozens of casualties. It's racing to identify more.