“More than 21 million Social Security numbers were compromised in a breach that affected a database of sensitive information on federal employees held by the Office of Personnel Management,” National Journal reports.  

“This hack is separate from the breach of OPM data that compromised 4.2 million Social Security numbers and was made public in June. Officials have privately linked both intrusions to China. Of the 21.5 million records that were stolen, 19.7 million belonged to individuals who had undergone background investigations, OPM said. The remaining 1.8 million records belonged to other individuals, mostly applicants’ families.”  

“The hack that resulted in the loss of these records began in May 2014, according to OPM Director Katherine Archuleta’s testimony before Congress. It was not discovered until May 2015… A security update applied by OPM and the Homeland Security Department in January ended the bulk of the data extraction… OPM said Thursday that individuals who underwent background investigations in or after the year 2000 are ‘highly likely’ to have had their information compromised in the breach.”