(USA TODAY) -- Chinese hackers broke into the federal Office of Personnel Management computer system in March, apparently targeting tens of thousands of employees who applied for top-security clearance,The New York Times is reporting.
TheTimes cites "senior American officials" and says a senior official with the Department of Homeland Security confirmed the attack but said authorities have not "identified any loss of personally identifiable information."
A senior official told the Times the breach had been tracked to China, but not necessarily the Chinese government.
China quickly dismissed the report Thursday, The Wall Street Journal reported. TheJournal quoted China Foreign Ministry spokesman Hong Lei, at his daily briefing, as saying China opposes hacker attacks.
"Some U.S. media and U.S. cybersecurity always smear China and create the theory that China is a cyberthreat, but they can't provide sufficient evidence of that," he said. "We feel strongly that these kinds of reports and comments are irresponsible and not worth a comment or refuting."
The hacking revelation comes as China's Communist Party leader Xi Jinping and U.S. Secretary of State John Kerry vowed better economic and security cooperation Wednesday in Beijing. The meeting was the latest in a series of talks designed to improve the sometimes tumultuous U.S.-China relationship.
Hacking has been a major point of contention in that relationship — with both sides accusing the other.
American officials told the Times the attack on the OPM was notable because hackers are always trying to breach government servers but seldom succeed.
Last year, the government acknowledged that hackers obtained employee and contractors' personal data at the Department of Energy. Agencies are compelled to reveal breaches in all cases involving personally identifiable information — but not in cases involving non-personnel-related government secrets.
"The administration has never advocated that all intrusions be made public," Caitlin Hayden, a spokeswoman for the Obama administration, said in a statement to theTimes. "We have advocated that businesses that have suffered an intrusion notify customers if the intruder had access to consumers' personal information. We have also advocated that companies and agencies voluntarily share information about intrusions."
In May, the Justice Department filed a 31-count indictment against five Chinese military officials operating under hacker aliases and accused them of penetrating computer networks of a half-dozen steel companies and makers of solar and nuclear technology to gain a competitive advantage. The Chinese government denied the allegations and suspended a working group on cyber rules that was to be part of the annual Strategic and Economic Dialogue this week.
The Office of Personnel Management houses personal information for all federal employees. Those applying for security clearances would be expected to provide such information as foreign contacts, previous jobs, past drug use and other personal details, the newspaper reported.
OPM also oversees a system by which federal employees applying for security clearances enter financial data and other personal information, the Times said, and those who maintain such clearances are required to update their information through that system. Agencies and contractors use the information to investigate employees.
Contributing: Associated Press