Washington (CNN) A federal grand jury has charged four members of the Chinese People's Liberation Army with hacking Equifax and stealing personal data and trade secrets in one of the largest hacks on record.

Attorney General William Barr said Monday that the scale of the theft in 2017 was "staggering" and the suspects obtained information for nearly 150 million Americans . The attorney general said the hack was one of the largest on record and was a "deliberate and sweeping intrusion into the private information of the American people."

Speaking at a news conference in Washington, Barr noted that it's unusual for the US to charge members of another country's military or intelligence service outside the US, but said the hack "not only caused significant financial damage to Equifax, but invaded the privacy of many millions of Americans, and imposed substantial costs and burdens on them as they have had to take measures to protect against identity theft."

"This data has economic value and these thefts can feed China's development of artificial intelligence tools as well as the creation of intelligence targeting packages," Barr said.

Equifax first disclosed the hack , the largest in US history, in September 2017, three months after the company discovered the breach. The hack exposed sensitive information, including names, Social Security numbers, driver's license numbers and addresses.

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