BEIJING // Chinese hackers repeatedly broke into The New York Times' computer systems during the past four months, the newspaper reported today.
The intruders stole reporters' passwords as they hunted for information about an investigation into the wealth amassed by the family of a top Chinese leader.
Security experts hired to find and plug the breach found the cyber attacks used tactics similar to ones used in previous hacking incidents traced to China.
The report said the hackers routed the attacks through computers at US universities, and installed a strain of malicious software, or malware, associated with Chinese hackers. The breaches were initiated from Chinese university computers previously used by the Chinese military to attack US military contractors.
The attacks, which began in mid-September, coincided with a Times investigation into how the relatives and family of the premier, Wen Jiabao, built a fortune worth more than US$2 billion (Dh7.3bn).
The story embarrassed Communist Party chiefs when it was posted online on October 25. It came ahead of a fraught transition to new leaders and exposed deep-rooted favouritism at a time when many people in China are upset about the wealth gap.
During the months of cyber-attacks, the hackers stole the passwords of all Times employees and used them to get into the personal computers of 53 employees.
The report said customer data was not compromised and that information about the investigation into the Wen family remained protected, though it left unclear what data or communications the infiltrators did manage to access.
"Computer security experts found no evidence that sensitive emails or files from the reporting of our articles about the Wen family were accessed, downloaded or copied," said Jill Abramson, an executive editor.
A Times spokeswoman declined to comment further.
The Chinese foreign and defence ministries called the Times' allegations baseless, and the defence ministry denied any involvement in the hacking by the military.
"Chinese law forbids hacking and any other actions that damage internet security," the ministry said. "The Chinese military has never supported any hacking activities.
"Cyber-attacks are characterised by being cross-national and anonymous. To accuse the Chinese military of launching cyber-attacks without firm evidence is not professional and also groundless."
China has been accused by the US, other foreign governments and computer security experts of mounting a widespread, aggressive cyber-spying campaign for several years, trying to steal classified information and corporate secrets and to intimidate critics.
Foreign reporters and news media have been among the targets of attacks intended to uncover the identities of sources for news stories, and to stifle critical reports about the Chinese government.
"Attacks on journalists based in China are increasingly aggressive, disruptive and sophisticated," said Greg Walton, a cybersecurity researcher who has tracked Chinese hacking campaigns. China's cyber-spying efforts have excelled in part because of the government's "willingness to ignore international norms relating to civil society and media organisations", he said.
The Times reported that executives became concerned just before the publication of the Wen investigation after learning that Chinese officials had warned of unspecified consequences.
Soon after the publication of the story, AT&T, which monitors the Times' computer networks, notified the company about activity consistent with a hacking attack, the report said.
After months of investigation by Mandiant, a computer security firm, experts were still unsure how the hackers initially infiltrated the newspaper's computer systems, the report said.