The Koch brothers, who control the second-largest privately held company in the United States, hired former NYPD commissioner Howard Safir to dig up dirt on journalist Jane Mayer, she claims in a new book.

Mayer, a staff writer for the New Yorker, says that soon after she revealed how David and Charles Koch were using their fortune to exert an outsize influence over American politics in a lengthy magazine expose titled “Covert Operations,” she found out that the brothers had assembled a team of operatives and private investigators to discredit her. One of them was Safir, who served as police commissioner under former New York City mayor Rudy Giuliani, she writes in her new book, Dark Money: The Hidden History of the Billionaires Behind The Rise of the Radical Right. Along with his son Adam Safir, Howard Safir currently runs Vigilant Resources International, a private investigative firm. Safir’s firm touts itself as adhering to the “highest standards of confidentiality and discretion.”

When Mayer—who profiles the Koch brothers and their “rebranding” again in this week’s New Yorker—confronted both Safirs, they each declined comment. Howard said, “I don’t confirm or deny it,” Mayer told Fast Company. A spokesman for Koch Industries also declined comment when asked by Mayer about both hiring Safir’s firm and launching an investigation into her.

‘Dirt, dirt, dirt’ is what the source later told me they were digging for in my life. ‘If they couldn’t find it, they’d create it.’

Some of Mayer’s revelations about the Kochs from Dark Money have made headlines, including the assertion that the family patriarch helped build a major oil refinery in Nazi Germany that was personally approved by Adolf Hitler. The Kochs have insisted that the refinery was built years before Germany invaded Poland and that the elder Koch stopped doing business in the country “when it became clear that Hitler’s government was a tyrannical regime.”

Other operatives reportedly tapped by Koch Industries to discredit Mayer and take on critics of the brothers were Michael Goldfarb (who worked for Sarah Palin’s vice-presidential campaign and later founded conservative publication The Washington Free Beacon) and Philip Ellender, who ran the company’s lobbying and public relations operations in Washington, D.C., reports Mayer.

Three blocks from the White House, about half a dozen operatives worked in office space in the back of former congressman J.C. Watts’s lobbying firm, Mayer says. “Their aim, according to a well-informed source, was to counteract The New Yorker’s story on the Koch brothers by undermining me. ‘Dirt, dirt, dirt’ is what the source later told me they were digging for in my life. ‘If they couldn’t find it, they’d create it.’” She learned from her own sources that “their search for dirt had started with my personal life, I was told, but when that turned up nothing truly incriminating, they moved on to plagiarism.”

Soon, Mayer and New Yorker editor David Remnick were contacted by a reporter for a conservative news site The Daily Caller, who accused her of plagiarism, a journalistic sin that can destroy a career. But the four examples didn’t hold up, especially since Mayer explicitly cited the authors whose work she was accused of ripping off in two cases, and three of the authors issued statements supporting Mayer.