After three months of accusations that Russia is seeking to influence the US presidential election with a cyber-hacking campaign, the US is planning to strike back and send “a message” to Moscow with “the greatest impact.”

In an Oct. 16 interview on the NBC show Meet the Press, vice president Joe Biden said that the US retaliation against Russian cyber attacks would be covert. The United States’ two main weapons against such cyber intrusions are sanctions and a reciprocal cyber attack, but sanctions are never covert and of dubious impact. So it seems likely from Biden’s remarks that the US is planning a demonstration of cyberspace might.

One likely tactic in a US cyber attack on Russia would be to threaten or actually release detailed accounts of Russian president Vladimir Putin’s wealth, intelligence that would have been gathered by the National Security Agency. Such a strategy could rattle Putin by potentially affecting his domestic popularity without damaging any infrastructure, and thus avert a dangerous escalation of hostilities.

“We’re sending a message. We have the capacity to do it. And the message—he’ll know it,” Biden said, referring to Putin. “And it will be at the time of our choosing. And under the circumstances that have the greatest impact.”

Biden’s remarks come a week after James Clapper, the director of US intelligence, formally accused Russia of attempting to influence the election.

The US began to notice massive Russian cyber-intrusions into government computers in early 2016 or before. They began telling reporters in July, after the release of 20,000 hacked emails from Democratic Party officials and consultants by WikiLeaks. Russian intelligence agencies—working through cyber hackers known as APT28 and Fancy Bear—gained access to the emails, in addition to others in the State Department, the White House, and other agencies.

The break-ins have continued through the presidential campaign. There also appears to be a channel from the hackers to WikiLeaks, whose founder Julian Assange has openly sought to help defeat Democratic nominee Hillary Clinton.