Upon hearing of the massive data breach of employee information from the Office of Personnel Management (OPM) ― allegedly by hackers working for the Chinese government ― Kay Coles James, the former director of OPM under George W. Bush, told me she was “aghast,” adding, “I can’t think about the national security implications of a foreign government knowing every single federal employee, where they work, where they live, all of their significant data.”

Joel Brenner, a former top counterintelligence official for the U.S. government, has thought about it. He called the hack attack “potentially devastating.” Mr. Brenner told The Washington Post that personnel files “contain decades of personal information about people with (security) clearances which makes them easier to recruit for foreign espionage on behalf of a foreign country.”

The Associated Press reported “two people briefed on the investigation disclosed Friday that as many as 14 million current and former civilian U.S. government employees have had their information exposed to hackers, a far higher figure than the 4 million the Obama administration initially disclosed.”

By some estimates there are thousands of Chinese cyberwarriors specifically trained to carry out electronic espionage against the United States and other nations with information the Chinese believe they can use for business, military and political purposes.

Under a worst-case scenario outlined by Theweek.com, the information obtained by hackers could be used to derail trains, disrupt air traffic control systems, explode chemical plants and gas pipelines and compromise electric grids, causing large-scale blackouts across the country. Who needs missiles when a laptop and the right software can be just as effective?

It doesn’t take a spy novelist to come up with a scenario in which a Chinese government agent approaches someone with a top security clearance and threatens to expose a dark secret in his past, possibly destroying family and career, unless he cooperates and hands over information to Beijing. The Chinese agent would likely have details about medications his target is taking to ward off depression, or some other malady, possibly making him more vulnerable to pressure.

The former chairman of the House Intelligence Committee, Mike Rogers, says another possible use of the hacked information could be to shape fake emails crafted to look legitimate while injecting spyware and other viruses into the networks of government agencies or businesses the Chinese wish to penetrate.