The US justice department announced charges on Monday against four members of the Chinese military over the 2017 hacking of a credit-reporting agency.
The four military personnel are being charged with counts of computer fraud, economic espionage and wire fraud, according to an indictment by a grand jury in Atlanta.
“This was a deliberate and sweeping intrusion into the private information of the American people,” said US attorney general William Barr in a statement.
The credit reporting agency Equifax announced in 2017 that hackers had stolen the personal data of roughly 145 million Americans - nearly half of the U.S. population - including names, social security numbers and birthdates.
Many also had their credit card numbers and addresses stolen.
Hackers had run about 9,000 queries on Equifax's system to obtain the sensitive information, the department said. The hackers routed traffic through roughly 34 servers in about 20 countries to conceal their location.
Barr said that the hacking fit a "disturbing and unacceptable pattern of state-sponsored computer intrusions and thefts by China".
The investigation was conducted jointly by multiple offices within the FBI and Department of Justice.
The Chinese foreign ministry spokesperson said in a statement that they "never engage in cyber theft of trade secrets" and accused the US of having a "double standard" on cybersecurity.
A US congressional oversight report released in 2018 said that the credit reporting agency had failed to "implement an adequate security program to protect this sensitive data".
The hacking resulted in several top executives leaving Equifax - one of the US' largest credit reporting agencies and the agency's settlement with the US government totalled about $700 million (roughly €640 million).
US social security, the post office and Internal Revenue Service all use Equifax identification services, the Government Accountability Office said in a report on the hack.
"Today's announcement is another positive step forward in helping us turn the page on the cybersecurity attack as we continue our focus on being a leader in data security," said the company's chief executive Mark W. Begor said in a statement after the charges were revealed. He emphasised that the company was spending over a billion US dollars to enhance security.
The indictment alleges that Wu Zhiyong, Wang Qian, Xu Ke and Liu Lei were "members of the PLA’s 54th Research Institute, a component of the Chinese military" and "conspired with each other" to hack into the Equifax computer networks.
"This is not the end of our investigation; to all who seek to disrupt the safety, security and confidence of the global citizenry in this digitally connected world, this is a day of reckoning," said FBI deputy director David Bowdich.
This article has been updated to add a response from the Chinese government.