Nearly 4 million US federal employees may have had their personal data breached by hackers. Anonymous sources say the source of the cyber-attack is China.
The US government said Thursday that it suspects hackers of accessing the personal data of four million current and former federal employees, with the origin of the attack believed to be China.
The breach was uncovered in April, and it was not immediately clear if senior government officials had been affected by the cyber-attack.
The US Office of Personnel Management, which handles hundreds of thousands of background investigations and security clearances on government employees each year, was the target of the attack. It said it "will send notifications to approximately four million individuals" affected by the breach.
US officials speaking anonymously told the Washington Post that the hack was carried out from China, making it the second Chinese cyber-attack on Washington in a year.
The data breach could potentially have exposed federal employee job assignments, training and performance ratings, but did not involve background or clearance investigations, the Washington Post reported.
The US Department of Homeland Security and the FBI are currently investigating the breach.
"The FBI is working with our interagency partners to investigate this matter," the bureau said in a statement. "We take all potential threats to public and private sector systems seriously, and will continue to investigate and hold accountable those who pose a threat in cyberspace."
The White House has not yet commented on the attack.
Breach 'among the most shocking'
Washington has long been wary of cyber spying and theft originating in China and has urged Beijing not to engage in such activities. China has denied US accusations of spying.
Representative Adam Schiff of the US House Permanent Select Committee on Intelligence warned the country must do more to enhance its cyber security.
"The last few months have seen a series of massive data breaches that have affected millions of Americans," Schiff said in a statement. He called the latest attack "among the most shocking because Americans may expect that federal computer networks are maintained with state of the art defenses."
"It's clear that a substantial improvement in our cyber databases and defenses is perilously overdue," Schiff said.
Federal employees will begin to be notified on June 8 if they have been affected by the breach.
bw/bk (Reuters, AFP, AP)