The FBI has launched its biggest transformation since the 2001 terror attacks to retrain and refocus special agents to combat cyber criminals, whose threats to lives, property and critical infrastructure have outstripped U.S. efforts to thwart them.

The push comes as federal investigators grapple with an expanding range of cyber attacks sponsored by foreign adversaries against businesses or national interests, including Russian election interference and Chinese cyber thefts from American companies, senior bureau executives said.

The Navy concluded recently that it was under “cyber siege” by China and others, and FBI Director Christopher Wray has said the agency has economic espionage investigations leading back to China open in all 56 bureau field offices.

“It’s very analogous to the shift after 9/11,” said Amy Hess, the new head of the Federal Bureau of Investigation’s criminal, cyber, response and services branch, in an interview. “I grew up in the FBI working criminal investigation—I worked violent crimes and gangs and drugs. And then, 9/11 happened. And we all, it felt like, were shifted to work terrorism. And so I think now, you’re seeing the same thing” with cyber security.

Data support the need for an across-the-board evolution at the FBI. Law-enforcement action is taken against less than 1% of malicious cyber incidents, according to an analysis of public data by Third Way, a center-left think tank in Washington. Investigations, as a result, typically only focus on the most severe cyber threats, such as nation-state attacks or sophisticated transnational crime.