Teams of technicians worked "round the clock" Saturday to restore hospital computer systems in Britain and check bank or transport services in other nations after a global cyberattack hit dozens of countries and crippled the U.K.'s health system.
The worldwide attack was so unprecedented that Microsoft quickly changed its policy and announced that it will make security fixes available for free for older Windows systems, which are still used by millions of individuals and smaller businesses.
In Russia, where a wide array of systems came under attack, officials said services had been restored or the virus contained.
The extortion attack, which locked up computers and held users' files for ransom, is believed to be the biggest of its kind ever recorded, disrupting services in nations as diverse as the U.S., Russia, Ukraine, Spain and India.
Europol, the European Union's police agency, said the onslaught was at "an unprecedented level and will require a complex international investigation to identify the culprits."
The ransomware appeared to exploit a vulnerability in Microsoft Windows that was purportedly identified by the U.S. National Security Agency for its own intelligence-gathering purposes and was later leaked to the internet.
