A United Kingdom report says a young cyber security researcher has been credited with helping to halt the spread of the global ransomware cyber-attack by accidentally activating a so-called "kill switch" in the malicious software. "Many of those will be businesses including large corporations".
The hackers are believed to have used "cyber weapons" stolen from the US' National Security Agency to lock up computers and hold users' files for ransom.
In the United Kingdom, a total of 48 National Health trusts were hit by Friday's cyber-attack, of which all but six are now back to normal, according to the Home Secretary Amber Rudd.
Attackers used ransomware that misused a security imperfection in Microsoft operating systems, securing clients' records unless they pay the hackers money in the virtual money Bitcoin.
The US Treasury Department said it will play a "leading role" in protecting the global financial system's IT infrastructure.
French carmaker Renault said this morning it was among those hit by the global ransomware cyber attack that has infected tens of thousands of computers in almost 100 countries.
He also said that this could be the most powerful cyber attack ever.
China's official Xinhua news agency said some secondary schools and universities had been affected, without specifying how many or identifying them.
But he also said he's concerned the authors of the malware could re-release it without a kill switch or with a better one, or that copycats could mimic the attack.
Dr Jakobsson said: "There's absolutely no excuse for any business not to have up to date systems".
The ransomware exploits a vulnerability in Microsoft Windows that was purportedly identified by the U.S. National Security Agency for its own intelligence-gathering purposes.
Microsoft says now it will make the fixes free for everyone. The bank network is protected from such attack. Microsoft swiftly released software "patches" to fix those holes, but many users still haven't installed updates or still use older versions of Windows.
An worldwide manhunt was well under way for the plotters behind the world's biggest-ever computer ransom assault.
France's carmaker Renault was forced to stop production at a number of sites.
Europol said a task force at its European Cybercrime Center was "specially created to assist in such investigations and will play an important role in supporting the investigation".
British Prime Minister Theresa May said there was no evidence patient data had been compromised and added that the attack had not specifically targeted the National Health Service.
TURKEY The head of Turkey's Information and Communication Technologies Authority or BTK says the nation was among those affected by the ransomware attack.
In addition to Russian Federation, the biggest targets appeared to be Ukraine and India, nations where it is common to find older, unpatched versions of Windows in use, according to security firms.
The Computer Emergency Response Team of Turkey tweeted that the "wannacry ransomware" is spread over Server Message Block flaws. "The work to eliminate it and upgrade anti-virus protection is now underway", they said in an official statement.
What occurred was an "indiscriminate attack across the world on multiple industries and services", Mr Wainwright said, including Germany's rail network Deutsche Bahn, Spanish telecommunications operator Telefonica, US logistics giant FedEx and Russia's interior ministry.
"For so many organisations in the same day to be hit, this is unprecedented", he said.