Of particular concern are federal contractors and subcontractors, who rarely get the same security training as federal employees, and in some scenarios don’t even know for what agency they are working. These employees are particularly ripe targets for highly sophisticated phishing emails that attempt to elicit sensitive corporate or government information.
The volume of data also allows the Chinese to do what the intell pros call “exclusionary analysis.” We’re told, for instance, that some highly sensitive agencies don’t send their background checks to OPM. So imagine a scenario in which the Chinese look through the names of 30 State Department employees in a U.S. embassy. Thanks to their hack, they’ve got information on 27 of them. The other three they can now assume are working, undercover, for a sensitive agency. Say, the CIA.