US officials security specialists warn that Russian hackers may answer new sanctions by attacking computer networks of US banks and large companies.
Officials involved in a White House review of the effects of further penalties on Russia did not respond to questions about whether the study explored the risk of cyberattacks. Even so, two sources said it included revisiting previous classified exercises in which small numbers of computer experts showed they were able to cripple the United States economy in a few days.
Cybersecurity specialists consider Russian hackers among the world's best at infiltrating networks and say evidence exists that they have already inserted malicious software on computers in the US.
The Financial Services Roundtable, an industry group that includes Citigroup and Bank of America, was watching for any signs of hacking attacks, although nothing appeared imminent, said Paul Smocer, head of the technology policy division of the Washington-based trade group.
"A cyberattack is a real concern that we all need to have," Smocer said. "Nation states' ability to launch cyberattacks is certainly real nowadays, and so in any conflict, I think that the possibility exists as we worry about escalation."
The US and its allies are preparing to impose additional sanctions on Russia this week over the conflict with Ukraine. The penalties may target individuals with influence in sectors of the Russian economy that include banking, White House deputy national security adviser Ben Rhodes said while accompanying President Barack Obama, who is travelling in Asia.
The Ukraine crisis intensified last week when Russian President Vladimir Putin warned the eastern European country that was part of the former Soviet Union to halt an offensive aimed at separatists. Ukrainian officials say Russia was helping fuel the separatist movement as part of efforts to destabilise the nation.
If Russia retaliates for sanctions on its banks and Putin associates, it could be difficult to trace any action to his government because hackers mask their identities and locations online.