The U.S. Office of Personnel Management is photographed Tuesday, Sept. 6, 2016, in Washington. It was time to purge the hacker from the U.S. government's computers. After secretly monitoring the hacker's online movements for months, officials worried he was getting too close to critical information and devised a plan to expel him. Trouble was, with all their attention focused in that case, they missed the other hacker entirely. A new congressional report provides previously undisclosed details and a behind-the-scenes chronology of one of the worst-ever cyberattacks on the United States, laying out missed opportunities before the break-in at the OPM exposed security clearances, background checks and fingerprint records. (AP Photo/Jacquelyn Martin)
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