Chinese hackers are once again believed to have successfully broken into American government computer networks, and the huge hack could potentially affect every single US federal agency, it was announced on Thursday.
Yet on Friday Beijing reacted to the allegations it was involved in the attack by saying such claims are unproven and irresponsible.
Foreign Ministry spokesman Hong Lei said at a news briefing Friday that China hopes the US would be "less suspicious and stop making any unverified allegations, but show more trust and participate more in cooperation."
"We know that hacker attacks are conducted anonymously, across nations, and that it is hard to track the source," Hong said. "It's irresponsible and unscientific to make conjectural, trumped-up allegations without deep investigation."
In a statement on Thursday, the Department of Homeland Security said that the federal government's human resources department, the Office of Personal Management (OPM), had been compromised, as well as the Interior Department. The attack is believed to have originated in China, according to lawmakers.
The OPM conducts the vast majority of federal background checks on would-be US government employees — and thus contains data from numerous government agencies. Some affected individuals may hold high-level state security clearances. Thus far, Washington has not revealed whether intelligence agency data was breached
"The FBI is conducting an investigation to identify how and why this occurred," said the Homeland Security statement.
Just a year ago, the OPM was targeted in another cyberattack that is also believed to have originated in China.
Indeed, US experts say that Chinese hackers are continuously working to breach American agencies and corporations. Adam Meyers, vice president for intelligence at the California-based company CrowdStrike, which monitors Chinese cyber activity, told the Associated Press that hackers may be hunting for vulnerable government employees who can be manipulated into handing over sensitive intelligence.
"If they know someone has a large financial debt, or a relative with a health condition or any other avenues that make them susceptible to monetary targeting or coercion, that information would be useful," Meyers said.
Shen Dingli, the director of Fudan University's Center for American Studies in Shanghai, said however: "Just don't pretend America is the only victim, America also victimizes others. The US government will target the Chinese government. If they happen to see the information of a few million Chinese government workers, would they not download it? I think they would."
The hack was detected by the Department of Homeland Security's EINSTEIN system, which screens government internet traffic. It is not clear why the system failed to detect the breach until after so many sensitive records were copied and removed.
Photo via [Wikimedia Commons_](https://commons.wikimedia.org/wiki/File:HK%E7%9F%B3%E5%A1%98%E5%92%80%E5%B8%82%E6%94%BF%E5%A4%A7%E5%BB%88_Shek_Tong_Tsui_Municipal_Services_Building_%E9%9B%BB%E8%85%A6%E9%8D%B5%E7%9B%A4_Chinese_input_keyboard_Jan-2012.jpg)
The Associated Press contributed to this report.