Todd Hemmen, deputy assistant director of the FBI's Cyber Capabilities Branch, disclosed the case on July 28 at a Digital Government Institute conference in Washington, in response to a question about whether North Korea's remote IT worker campaign had reached government.

He said the bureau had identified the worker the week before but did not identify the agency or describe the worker's duties, according to Federal News Network, which reported his remarks on Aug. 11.

Hemmen said he was still working through the case and called it "a little bit baffling," telling the panel he did not understand the hiring process at the agency involved.

How the worker passed vetting and whether he reached sensitive systems or data have not been disclosed.

Federal investigators say North Korea has sent thousands of skilled IT workers around the world to obtain jobs fraudulently and generate revenue for its weapons programs, placing them inside hundreds of companies.