A new report on one of the worst cyberattacks on the U.S. is out, and it details missed opportunities to stop them.

FOX's Tonya J. Powers has more:

A congressional report says while government officials were focused on purging one hacker from its computers at the Office of Personnel Management, it missed a different hacker entirely.

The report, from the House Committee on Oversight and Government Reform, outlines previously undisclosed details of the 2014 cyberattack that compromised the personal information of more than 21 million current, former and prospective federal employees.

It says had security measures put in place earlier, the hack could have been prevented.

The acting director of the OPM says the agency disagrees with the report.

Tonya J. Powers, FOX News.

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