Senior White House cybersecurity official Anne Neuberger said on Monday that important U.S. companies that provide critical infrastructure should improve their cyber defensive posture because of ongoing digital threats from Russia.

Neuberger said the U.S. government has seen "preparatory" Russian hacking activity aimed at numerous U.S. companies, but it has "no certainty" such attacks will occur.

The administration recently provided classified briefings to hundreds of U.S. companies that may be targeted by Russian hackers, Neuberger said.

The White House also published a written statement on Monday from President Joe Biden where he warned that Moscow may lash out with cyberattacks because of the "unprecedented economic costs we’ve imposed on Russia."

This warning, Neuberger said, is based on "evolving threat intelligence."