Our Revolution, the progressive advocacy organization the grew out of Bernie Sanders' 2016 presidential campaign, has publicly acknowledged that a sophisticated hacking and theft operation last year stole nearly a quarter of million dollars from the group—funds it has been unable to recover.

According to Politico, which obtained tax filings that revealed the incident:

Our Revolution "was the victim of a Business E-Mail Compromise scam that took place in December 2016 but was not discovered until January 2017, resulting in the loss of approximately $242,000 via an electronic transfer of funds to an overseas account," the group disclosed in its tax forms covering the year 2017, which were filed earlier this month. "Our Revolution worked with the Federal Bureau of Investigation, Our Revolution's counsel and an independent cyber-security consultant in an effort to identify the thieves and to recover the funds but, unfortunately, these efforts were unsuccessful."

The money stolen from the compromised account had been raised for the Standing Rock Sioux Native American tribe, which was at the time fighting vigorously to stop the construction of the Dakota Access Pipeline.

Lucy Flores, a former Our Revolution board member, told Politico that the organization still gave the tribe the $242,924 it had raised on its behalf, though it was forced to dip into other funds to do so.

"We'd done fundraising specifically on behalf of the tribe, and to have that money just be gone and never reach its intended purpose was unacceptable," Flores said. "So we decided to give them the money that was raised and take the loss as an organization."

Citing the FBI, Politico reports the type of hack used against the group is known as a "CEO impersonation," one in which the attackers get inside a computer network and then create fake requests for wire transfers that look legitimate, usually by impersonating a known vendor. This kind of tactic—used against individiduals, organizations, and businesses—results in billions of dollars in losses each year.

After the theft was detected, said Our Revolution president Nina Turner, "we hired a cybersecurity firm to advise us on how to prevent these types of crimes in the future."