The extortion attack, also called ransomware, used "WannaCry" malware that encrypts users' files until users pay a ransom.
Darien Huss, a senior security research engineer at Proofpoint, warned that "a new attack" was a major concern following the first cyber assault.
In response, cyber spies around the world are calling on the skills of bedroom computer prodigies such as the 22-year-old surfer credited with helping to stop Friday's attack.
On Sunday night, Microsoft slammed the U.S. spy agency that had originally developed software that allowed the ransomware attack to infect computers.
Over 200,000 infections in at least 150 countries have been recorded, including one in a system in a voluntary run healthcare facility in Wexford, which has been isolated.
A spokesperson said: 'We remain vigilant in alerting NHS organisations to known cyber security threats and advising them of appropriate steps to take to minimise these risks; in addition to protective near real time monitoring of national NHS IT services and systems, which are unaffected by this issue.
"With access to and the use of vast quantities of personal data, public bodies must have in place robust data protection plans, ensure access to expert support and not to cut cyber security resources when efficiencies are needed elsewhere".
When asked if the government ignored warnings that the NHS could be vulnerable to cyber attacks, Prime Minister Theresa May told Sky News that the United Kingdom healthcare system was given ample warning about the risks posed by out-dated systems.
NHS Digital said health trusts across England were sent details of an IT security patch that would have protected them from the attack.
"It is important to note that the vast majority of NHS organizations report that they are running contemporary IT systems, which are commissioned depending on local need", the NHS said in a statement.
The computers were locked down in exchange for ransom payments, said Mashable.
- How did the attack spread worldwide? That prompted the company to issue another patch on Friday for older and unsupported operating systems such as Windows XP, allowing users to secure their systems without requiring an upgrade to the latest operating software.
He added: "Although we have never seen anything on this scale when it comes to ransomware attacks, they are relatively common and there are things that you can do, that everyone can do, all of us can do, to protect ourselves against them".