Cybersecurity

NSA officials worried about the day its potent hacking tool would get loose. Then it did.

When the National Security Agency began using a new hacking tool called EternalBlue, those entrusted with deploying it marveled at both its uncommon power and the widespread havoc it could wreak if it ever got loose.

Some officials even discussed whether the flaw was so dangerous they should reveal it to Microsoft, the company whose software the government was exploiting, according to former NSA employees who spoke on the condition of anonymity given the sensitivity of the issue.

But for more than five years, the NSA kept using it — through a time period that has seen several serious security breaches — and now the officials’ worst fears have been realized. The malicious code at the heart of the WannaCry virus that hit computer systems globally late last week was apparently stolen from the NSA, repackaged by cybercriminals and unleashed on the world for a cyberattack that now ranks as among the most disruptive in history.