On Sept. 7, 2017, the world heard an alarming announcement from credit ratings giant Equifax: In a brazen cyberattack, somebody had stolen sensitive personal information from more than 140 million people, nearly half the population of the U.S. The information included Social Security numbers, driver's license numbers, information from credit disputes and other personal details. Then, something unusual happened. The data disappeared. Completely. CNBC talked to eight experts. All of them agreed that a breach happened, and personal information from 143 million people was stolen. But none of them knows where the data is now. Security experts haven't seen the data used in any of the ways they'd expect in a theft like this - not for impersonating victims, not for accessing other websites, nothing. Most experts familiar with the case now believe that the thieves were working for a foreign government and are using the information not for financial gain, but to try to identify and recruit spies. One former senior intelligence official ... summarized the prevailing expert opinion on how the foreign intelligence agency is using the data. First, he said, the foreign government is probably combining this information with other stolen data, then analyzing it using artificial intelligence or machine learning to figure out who's likely to be - or to become - a spy for the U.S. government. Second, credit reporting data provides compromising information that can be used to turn valuable people into agents of a foreign government.