The director of the Office of Personnel Management underwent another grilling Wednesday, this time from members of the House Oversight and Government Reform Committee. Katherine Archuleta sat for more than three hours as lawmakers questioned her competence and her estimates of how many government workers may have had their data breached in the hacking of OPM's computers discovered this spring.

NPR, along with other news organizations, has reported the hack may have exposed the personal data of more than 18 million current and former government workers. But Archuleta told lawmakers that 18 million "refers to a preliminary, unverified, and approximate number of unique Social Security numbers," adding "it is a number that I am not comfortable with."

Archuleta stood by earlier estimates that 4.2 million current and former government employees' data was exposed. Committee chairman Jason Chaffetz, R-Utah, wondered if the number "could be as high as 32 million."

That was a reference to OPM's budget request in which it stated it has records for 32 million current and former employees.

Archuleta reiterated that she was not going to "give you a number that I am not sure of."

Other members of the panel expressed anger at the way government employees have been treated and informed their data may be at risk. Chaffetz reiterated his call for Archuleta to step down, telling her, "I think you're part of the problem." He also called for OPM Chief Information Officer Donna Seymour's resignation, telling her, "I think you're in over your head."

But Gerald Connolly, D-Va., came to Archuleta's defense, saying "it's easy to make a scapegoat out of somebody," but what the government is facing is "a much bigger threat than a management snafu."

Connolly said the U.S. is "facing a systematic, organized, financed, pernicious campaign by the Chinese government ... to penetrate our cyber world."

Blaming Archuleta for the breach, he said, "is to miss the big picture."

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