The Biden administration in classified briefings last week and publicly on Monday urged critical infrastructure entities to ensure they are doing all they can to protect themselves from cyber-attacks and the president warned that Russia is mulling its options on the cyber front.

“This is a critical moment to accelerate our work to improve domestic cybersecurity and bolster our national resilience,” President Biden said in a statement. “I have previously warned about the potential that Russia could conduct malicious cyber activity against the United States, including as a response to the unprecedented economic costs we’ve imposed on Russia alongside our allies and partners. It’s part of Russia’s playbook. Today, my administration is reiterating those warnings based on evolving intelligence that the Russian government is exploring options for potential cyberattacks.”

There is no identified specific threat at the moment, Anne Neuberger, deputy national security adviser for cyber and emerging technology, said at a White House briefing on Monday afternoon. She described the activity that the U.S. has seen as “preparatory,” such as hunting for vulnerabilities and scanning websites. She also warned of known vulnerabilities that need to be patched.

The preparatory activity was shared with “several hundred companies” and critical infrastructure sectors in classified briefings last week and included the government providing “very practical, focused advise,” she said.

Monday’s announcement was aimed at creating greater awareness of the potential threat and a “call to action,” Neuberger said.

Last Thursday, the FBI and the Department of Homeland Security’s Cybersecurity and Infrastructure Security Agency issued a joint cybersecurity advisory warning of potential threats to U.S. and international satellite communications networks. In late February when Russia launched its invasion of Ukraine, global communications satellite provider Viasat [VSAT] was victimized by a cyber-attack that impacted its customers in Europe and Ukraine.

Neuberger said the U.S. hasn’t identified who’s behind the attack “but we’re carefully looking at it.”

The U.S. has made previous warnings to domestic critical infrastructures about potential Russian cyber-attacks in response to the ongoing war in Ukraine but still hasn’t seen any cyber-attacks by Russia against the U.S. The latest warning “speaks to evolving threat intelligence and a potential shift in intention to do so,” she said.

Russia continues to carry out cyber-attacks against Ukraine, Neuberger said.