More than 200,000 victims in around 150 countries have been infected by the ransomware which originated in the United Kingdom and Spain on Friday before spreading globally.
The so-called WannaCry ransomware locks access to user files and in an onscreen message demands payment of $300 in the virtual currency Bitcoin in order to decrypt the files.
Europol executive director Rob Wainwright had warned yesterday the situation could worsen when workers return to their offices on Monday after the weekend and logged on.
At current standing more than 200,000 computers across 150 countries have been attacked, with Russian Federation and Britain among the worst hit.
"And it's why we've pledged our support for defending every customer everywhere in the face of cyber-attacks, regardless of their nationality".
"Bearing in mind the impact of the global cyber-attack, we would urge people to be patient with NHS staff who may still be dealing with disruption on Monday".More news: Former Real Madrid defender: Zidane already a great coach
"Unfortunately, there are some very smart and bad people out there who spend their times trying to make things worse for us, and this is not game over for us", he said.
According to reports, ATMs or automated teller machines are highly vulnerable to such malware attacks as they now run on old version of Microsoft's Windows operating system, making a software security patch update a necessary exercise.
In England, 48 National Health Service (NHS) trusts reported problems at hospitals, doctor surgeries or pharmacies, and 13 NHS organizations in Scotland were also affected.
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It says universities and educational institutions were among the hardest hit, numbering 4,341, or about 15 percent of internet protocol addresses attacked.
It compared it to the U.S. military having some of its Tomahawk missiles stolen.More news: Emmanuel Macron, youngest French leader since Napoleon, sworn in
The attack is unique, according to Europol, because it combines ransomware with a worm function, meaning once one machine is infected, the entire internal network is scanned and other vulnerable machines are infected.
The ransomware tracker counts the volume of queries made to MalwareTech's registered domain, which is a fundamental part of WannaCrypt's operations; the ransomware abandons its attack if it can connect to the previously unregistered domain.
Cyber security experts have warned that the ransomware virus, which affected one in five NHS trusts, could be reactivated by computers and devices that have not yet been switched on. He added: "The governments of the world should treat this attack as a wake-up call". The British Home Secretary said most of the NHS systems were back to normal by midday Saturday.
Other organisations targeted include Germany's rail network Deutsche Bahn, Spanish telecommunications operator Telefonica, French carmaker Renault, US logistics giant FedEx and Russia's Interior Ministry.
Symantec said the majority of organisations affected were in Europe.
Eleven area health boards were affected, as were NHS National Services and the Scottish Ambulance Service.More news: Man United, Ajax advance to Europa League final