The head of the U.S. National Security Agency has warned that hackers will inevitably attack U.S. infrastructure in an attempt to cause a power failure like the one in Ukraine last year.
Admiral Michael Rogers told a cybersecurity conference in San Francisco that it is a "matter of when, not if" a foreign state launches a cyberattack on U.S. targets.
"An actor penetrated the Ukrainian power grid and brought large segments of it offline in a very well-crafted attack that both focused on knocking the system down but also focused on how was the provider likely to respond to that outage," Rogers said.
"Seven weeks ago, it was Ukraine. That isn't the last we are going to see of this, and that worries me."
Rogers said he is also worried about potential cyberthreats by terrorist groups such as Islamic State.
The U.S. government last week confirmed that a December 23 blackout in Ukraine that affected 225,000 customers was the result of a cyberattack.
Private researchers have linked the incident to a Russian hacking group known as "Sandworm."