The incident was perhaps the most high-profile computer-worm outbreak in nearly a decade, disrupting a wide range of corporations, hospitals and government agencies, from French car manufacturerRenault SA &U.S. FedEx Corp.to the Russian Interior Ministry. It took advantage of security vulnerabilities in Microsoft Corp.software that was either too old to be supported by security patches, or hadn’t been patched by users. The malware scrambled files of infected computers, then promised to restore the files after ransom payments by bitcoin of as little as $300 each. Security experts have been able to track a small amount of bitcoin transaction they say is linked to the attack and likely ransom. But it was impossible to say how many companies were paying.
The U.K. government said it had advised the National Health Service not to pay any ransom.