In China, hundreds of thousands of computers at almost 30,000 institutions and organisations were infected by late Saturday, internet firm 360 Security said. Back up your data on an offline hard drive. 4. It said it believed the difficulties are linked to the global cyberattack but they haven't so far harmed its business operations. Most stations had recovered. Programmes were being installed to fix the problem.
The Japan Computer Emergency Response Team Co- ordination Centre said 2,000 computers at 600 companies in Japan had been affected.
But computers and networks that didn't update their systems remained at risk.
Symantec said the majority of organisations affected were in Europe.
Citing the far-reaching potential impact on customers, Microsoft took the unusual step of offering a custom support security update for users with versions of Windows that are no longer supported.
Meanwhile health authorities were racing to upgrade outdated security software amid fears hackers could exploit the same vulnerability with a new virus. "We have seen vulnerabilities stored by the Central Intelligence Agency show up on WikiLeaks, and now this vulnerability stolen from the NSA has affected customers around the world", Smith wrote. An equivalent scenario with conventional weapons would be the USA military having some of its Tomahawk missiles stolen.
"The ransomware also spreads through malicious attachments to emails", it said.
"The numbers are still going up", he said.
NHS organisations across the country are warned that this software is likely to hit again today as staff return to work.
Apple's Mac computers were not targeted by this ransomware attack.
"If there is a lesson from that", Singer said, it's that "you want to enable security research and information exchange".
He says if a new variant without a so-called kill switch pops up, then organizations will be on their own to prevent it from taking over their computers. "There were the same attacks applied to Nissan on Friday and in other areas of the economy and indeed around the world", Fallon said.
The impact of Friday's global cyber attack is feared to continue to have an impact today, as workers switch on their computers for the first time since before the weekend.
The British government said 48 of 248 health service trusts - the bodies that run the hospitals - in England had been impacted by Friday's attack.
A huge extortion cyber attack had hit dozens of nations on Saturday, holding computer data for ransom at hospitals, telecommunications firms and other companies.
The ransomware virus is such lethal and smart that "it also drops a file named '!Please Read Me!.txt' which contains the text explaining what has happened (to the computer) and how to pay the ransom".
In light of the recent WannaCry (WannaCrypt) ransomware attacks, which saw an NSA-owned virus stolen and used in an attack that brought United Kingdom hospitals to its knees, Microsoft has issued a asking for "a new Digital Geneva Convention" to avoid the hoarding of malicious vulnerabilities by government agencies.
However, Wainwright said so far "remarkably few" payments had been made by the victims of the attack.
He said it was too early to say who is behind the onslaught and what their motivation was. "Most of the reported cases of payment of ransom are from overseas".
Shanghai's Fudan University received reports that a large number of school computers were infected with the virus.
"This is a virus that attacked Windows platforms". It locks users' files and demands a $300 (£230) payment to allow access.
WannaCry takes advantage of a vulnerability in Microsoft Windows. WannaCry exploited common techniques employees use to share files via a central server.
"We've never seen anything like this", the head of the European Union's policing agency told Britain's ITV television Sunday, calling its reach "unprecedented".