The Obama administration on Thursday announced what appeared to be one of the largest breaches of federal personnel data, involving at least four million current and former government employees, in an intrusion that federal officials say apparently originated in China.
The personal data was held by the Office of Personnel Management, which handles government security clearances and federal employee records. The breach was detected in April, the office said, but it appears to have begun at least late last year.
The breach is the second major foreign intrusion into an important federal computer system in recent months. Last year, the White House and the State Department found that their email systems had been compromised in an attack that has been widely attributed to Russian hackers.