China Says U.S. Allegations That It Was Behind Cyberattack Are 'Irresponsible'

Updated at 5:25 p.m. ET

The Chinese government says U.S. allegations that China is behind a massive cyberattack against the Office of Personnel Management are "counterproductive" and "irresponsible."

As we reported Thursday, the U.S. government said that a data breach in April may have exposed the personal information — names and Social Security numbers, birthdates — of nearly 4 million past and current federal employees.

Anonymous U.S. officials told several news outlets that authorities believed the attack originated in China, but they were still investigating whether it was state-sponsored. Sen. Susan Collins told The Associated Press the same thing, but added that the breach was "yet another indication of a foreign power probing successfully and focusing on what appears to be data that would identify people with security clearances."

The Chinese government quickly responded to the allegations. Xinhua, the state-run news agency, reported that the Chinese embassy in Washington warned of "jumping to conclusions."

"Cyber attacks conducted across countries are hard to track and therefore the source of attacks is difficult to identify. Jumping to conclusions and making hypothetical accusation is not responsible and counterproductive," Zhu Haiquan said, according to Xinhua.

The AP reports that this morning Chinese Foreign Ministry spokesman Hong Lei was on the defensive, echoing what the embassy said Thursday.

"It's irresponsible and unscientific to make conjectural, trumped-up allegations without deep investigation," Hong said at a briefing.

Meanwhile, the U.S. is trying to pick up the pieces. The New York Times reports:

"The personnel office told current and former federal employees that they could request 18 months of free credit monitoring to make sure that their identities had not been stolen, and it said it was working with cybersecurity specialists to assess the effects of the breach. It was clear, however, that the scope was sweeping, potentially affecting a vast majority of the federal work force. J. David Cox Sr., the president of the American Federation of Government Employees, said he had been told that the breach might have affected 'all 2.1 million current federal employees and an additional two million federal retirees and former employees.' ...

"The attack drew calls for legislation to bolster the nation's cyberdefenses. In a series of Twitter posts, Representative Adam B. Schiff of California, the senior Democrat on the Intelligence Committee, called the intrusion 'shocking because Americans may expect that federal computer networks are maintained with state of the art defenses.' "

And, as NPR's Brian Naylor reported on All Things Considered, White House spokesman Josh Earnest said the hack occurred late last year:

"Earnest said officials believe the attacks had begun in December. They were discovered in April. And it wasn't until last month that it was determined the hackers made off with employees personal data. Its clear the OPM computers are an inviting target. OPM acts as governments HR department, and conducts background checks on employees who need security clearances. Their computers are subject to an estimated 2 and a half billion attacks every month. "

And Earnest said "it's not clear yet" who the perpetrators are behind the attack.