A hacker recently infiltrated 10,000 websites on the Dark Web. NBC News

The election is over, but Russian hackers are now extorting left-wing groups, a recent Bloomberg report said.

At least a dozen U.S. progressive groups have been targeted since the election, sources familiar with investigations being carried out by the FBI and private security firms told Bloomberg. The hackers are stealing organizations' emails and documents and using the material as an attempt to get money from the groups.

Some of them have paid the ransoms requested, even though there is a small possibility the documents won’t be made public anyway, the report said. Russian hackers have asked for amounts ranging from $30,000 to $150,000. The ransom was supposed to be payable in untraceable bitcoins.

The alleged extortions on progressive groups come after questions about whether Russian hackers affected the 2016 U.S. presidential election. Top U.S. intel officials believe Russia hacked Democrats to help President Donald Trump win the election last November.

The hackers are using techniques similar to those of Cozy Bear, the state-backed group believed to be involved in the Democratic National Committee hacks last year.

The report named two organizations that had been targeted, the Center for American Progress and Arabella Partners. According to the sources, it is not clear whether Arabella was part of the same campaign as the other dozen organizations, but the tactics are similar.

“Arabella Advisors was affected by cyber crime,” a spokesman for the firm told Bloomberg. "All facts indicate this was financially motivated.’’

Meanwhile, the Center for American Progress said it had not been hacked.