SAN FRANCISCO — The question is no longer who has been hacked. It’s who hasn’t?
The Washington Post can be added to the growing list of American news organizations whose computers have been penetrated by Chinese hackers.
After The New York Times reported on Wednesday that its computers as well as those of Bloomberg News had been attacked by Chinese hackers, The Wall Street Journal said on Thursday that it too had been a victim of Chinese cyberattacks.
According to people with knowledge of an investigation at The Washington Post, its computer systems were also attacked by Chinese hackers in 2012. A former Post employee said there had been hacking attempts at the Washington Post for at least four years, but none targeted the company’s newsroom. Then, last year, newsroom computers were found to be communicating with Web servers that were traced back to China, according to people with knowledge of the Post investigation who declined to speak on the record.
Jennifer Lee, a spokeswoman for the Post Company, said that the “company did not have anything to share at this time.”
Security experts said that in 2008, Chinese hackers began targeting American news organizations as part of an effort to monitor coverage of Chinese issues.
In a report for clients in December, Mandiant, a computer security company, said that over the course of several investigations it found evidence that Chinese hackers had stolen e-mails, contacts and files from more than 30 journalists and executives at Western news organizations, and had maintained a “short list” of journalists for repeated attacks.
Among those targeted were journalists who had written about Chinese leaders, political and legal issues in China and the telecom giants Huawei and ZTE.
The Times reported on Wednesday that Bloomberg L.P. was also attacked by Chinese hackers after its Bloomberg News unit published an article last June about the wealth accumulated by relatives of Xi Jinping, China’s vice president at the time. Mr. Xi became general secretary of the Communist Party in November and is expected to become president in March.
The secretary of state, Hillary Rodham Clinton, said on Thursday that a global effort was needed to establish rules for cyberactivity. In her final meeting with reporters, Mrs. Clinton addressed a question about China’s efforts to infiltrate computer systems at The New York Times. “We have seen over the last years an increase in not only the hacking attempts on government institutions but also nongovernmental ones,” she said, adding that the Chinese “are not the only people who are hacking us.”