“Arabella Advisors was affected by cyber crime,” said Steve Sampson, a spokesman for the firm, which lists 150 employees operating in four offices. "All facts indicate this was financially motivated.’’

Stealing Documents

During the election Russian hackers heavily targeted the personal email accounts of staffers associated with the Clinton campaign. One of the people who described the current campaign said that in some cases, web-based email accounts are also being targeted because of their heavy use among non-profits.

Along with emails, the hackers are stealing documents from popular web-based applications like SharePoint, which lets people in different locations work on Microsoft Office files, one of the people said.

The Federal Bureau of Investigation declined to comment when asked about the latest hacks. It is continuing to investigate Russia’s attempts to influence the election and any possible connections to Trump campaign aides. Russian officials have repeatedly denied any attempt to influence the election or any role in related computer break-ins.

“I would be cautious concluding that this has any sort of Russian government backing,” said John Hultquist, director of cyber espionage analysis at FireEye Inc., after the outline of the attacks was described to him. “Russian government hackers have aggressively targeted think tanks, and even masqueraded as ransomware operations, but it’s always possible it is just another shakedown.”

Left-Leaning Groups

The hackers’ targeting of left-leaning groups -- and the sifting of emails for sensitive or discrediting information -- has set off alarms that the attacks could constitute a fresh wave of Russian government meddling in the U.S. political system. The attacks could be designed to look like a criminal caper or they could have the tacit support of Russian intelligence agencies, the people said.

Russia’s intelligence agencies maintain close relationships with criminal hackers in the country, according to several U.S. government investigations.

None of the possible explanations for the attacks are particularly comforting to the victimized groups, few of which are household names but are part of the foundation of liberal politics in the U.S.