Chinese hackers repeatedly penetrated The New York Times’ computer systems over the past four months, AP reports. The hackers stole reporters’ passwords and hunted for files on an investigation into the wealth amassed by the family of a top Chinese leader.

Security experts hired to investigate and plug the breach found that the attacks used similar tactics to the ones used in previous hacking incidents traced to China. The hackers routed attacks through U.S. university computers, installed a strain of malicious software (malware) associated with Chinese hackers and initiated the attacks from university computers previously used to attack U.S. military contractors, AP reports.

The attacks began in mid-September, which coincided with a Times investigation into how the relatives and family of Premier Wen Jiabao built a fortune worth more than $2 billion. The report, which was published online October 25, embarrassed Communist Party leadership, “coming ahead of a fraught transition to new leaders and exposing deep-seated favoritism at a time when many Chinese are upset about a wealth gap,” the article says.

Over the months of cyber-incursions, the hackers lifted the computer passwords of all Times employees and used them to get into the personal computers of 53 employees, AP reports. None of the Times’ customer data was compromised, and information regarding the investigation remained protected.

A report from the Times quoted the Defense Ministry as saying that Chinese law prohibits hacking and other acts that damage Internet security and that accusing it of “cyber-attacks without solid proof is unprofessional and baseless.”

According to AP, “China has been accused by the U.S., 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.”