A cyber-attack that has hit 150 countries since Friday should be treated by governments around the world as a “wake-up call”, Microsoft says.
It blamed governments for storing data on software vulnerabilities which could then be accessed by hackers.
It says the latest virus exploits a flaw in Microsoft Windows identified by, and stolen from, US intelligence.
There are fears of more “ransomware” attacks as people begin work on Monday, although few have been reported so far.
Many firms have had experts working over the weekend to prevent new infections. The virus took control of users’ files and demanded $300 (£230) payments to restore access.
The spread of the virus slowed over the weekend but the respite might only be brief, experts have said. More than 200,000 computers have been affected so far.
But on Monday South Korea said just nine cases of ransomware had been found, giving no further details.
Australian officials said so far only three small-to-medium sized businesses had reported being locked out of their systems while New Zealand’s ministry of business said a small number of unconfirmed incidents were being investigated.
In Japan, both Nissan and Hitachi reported some units had been affected, while in China energy giant PetroChina said that at some petrol stations customers had been unable to use its payment system.
‘Like stealing Tomahawks’
A statement from Microsoft president and chief legal officer Brad Smith on Sunday criticised the way governments store up information about security flaws in computer systems.
“We have seen vulnerabilities stored by the CIA show up on WikiLeaks, and now this vulnerability stolen from the NSA has affected customers around the world,” he wrote.
“An equivalent scenario with conventional weapons would be the US military having some of its Tomahawk missiles stolen.”
He added: “The governments of the world should treat this attack as a wake-up call.”
The organisation also said that many organisations had failed to keep their systems up to date, allowing the virus to spread.
Microsoft said it had released a Windows security update in March to tackle the problem involved in the latest attack, but many users were yet to run it.
“As cybercriminals become more sophisticated, there is simply no way for customers to protect themselves against threats unless they update their systems,” Mr Smith said.