Russian hackers are targeting U.S. progressive groups in a new wave of attacks, scouring the organizations' emails for embarrassing details and attempting to extract hush money, according to two people familiar with probes being conducted by the FBI and private security firms.

At least a dozen groups have faced extortion attempts since last year's U.S. presidential election, said the people, who provided broad outlines of the campaign. The ransom demands are accompanied by samples of sensitive data in the hackers' possession.

In one case, a nonprofit group and a prominent liberal donor discussed how to use grant money to cover some costs for anti-Trump protesters. The identities were not disclosed, and it's unclear if the protesters were paid.