The problem comes from older versions of Windows or those without Windows Updates, as these were not patched by Microsoft and were left open to attacks. Two hospitals in Indonesia were infected, resulting in patient files being held for ransom.
That being said, seven of the 47 of Britain's National Health Service trusts that were affected on Friday were still having IT troubles on Monday.
Security firms are encouraging companies and users to make sure they install the official patch from Microsoft.
Concerns were raised more NHS services could be affected on Monday, but Kent's hospital trusts confirmed they had not been targeted in the scam, thought to have accessed computers via email.
"There are clearly going to be some small businesses impacted ... but as a whole of nation, we can be confident so far that we've missed the worst of this".
The ransomware locks users' files and demands a United States dollars 300 payment to allow access.
Twitter users around the world posted complaints about their computers shutting down and posted photos of the ransom demands on their computer screens. The path to upgrading things hasn't been as rapid in places like China and Russian Federation. Security firms say Russian Federation was the country that was hit the hardest.
In April, a group known as Shadow Brokers leaked NSA tools that were used to attack and break into Windows computers.
"NCSC and NCA are working with Europol and other global partners to make sure we all collect the right evidence, which we need to do to make sure we have the right material to find out who has done this and we go after them". That amount is expected to increase. According to a Lakeridge spokesperson, however, the hospital's antivirus system was able to disable the ransomware.
Dr Dreyfus said Windows computers that don't have the latest security patches were vulnerable to the bug, urging Australians to ensure their antivirus software was up to date.
Experts said the ransomware programme appears to support dozens of languages, showing that the hackers wanted to corrupt networks worldwide.
Whenever Microsoft learns of vulnerabilities with its operating systems (OS) it releases a Security Update.
The fact is that poorly protected encryption or outdated systems are deplorably prepared to deal with a new class of cybercriminals, thereby enabling access to patients' medical data, which is supposed to be confidential and intensely personal, and other crucial data such credit card numbers, patients' medical bills and other important informations apart from behemoth payouts.
IT administrators and cyber security experts are on high alert this morning as people return to work three days after malicious software began causing extensive damage around the globe.