Cyber security experts predict that the scope of the attack could expand as people return to work and resume their work on computers, CNN reported on Monday.
Professor Clark said ransomware represented a growing threat to computer users but pointed out that this virus was not new and a "patch" had already been completed to protect newer operating systems but not "obsolete" ones like Windows XP.
Computers around the globe were hacked beginning on Friday using a security flaw in Microsoft's Windows XP operating system, an older version that was no longer given mainstream tech support by the USA giant.
How many countries were affected?
Following the ransomware cyber attack on Friday May 12 which affected the NHS and is believed to have spread through organisations in at least 74 countries worldwide, the National Fraud Intelligence Bureau has urged both individuals and businesses to follow protection advice immediately and in the coming days.
Ms Robinson said cyber attacks reinforced the need for everyone to guard against future incidents. Russia's Interior Ministry and companies including Spain's Telefonica, FedEx Corp.in the USA and French carmaker Renault all reported troubles.
It comes amid warnings that the crisis could spread to other sectors, with a wider "escalating threat" as millions of workers switch on their computers.
"Even if a fresh attack does not materialise on Monday, we should expect it soon afterwards", she said.
"It's important to understand that cyber attacks can be different from other forms of crime in that their sometimes highly technical and anonymous nature means it can take some time to understand how it worked, who was behind it and what the impact is", he told the BBC.
The computer can be infected by taking advantage of a Windows vulnerability that Microsoft (MSFT, Tech30) released a security patch for in March and computers that hadn't updated were still at risk.
But what exactly is it, how does it work and - most importantly - how can you keep yourself safe from attack?
Colleges: Internet security firm Qihoo360 issued a "red alert" over the weekend, saying a large number of colleges and students in China had been hit by the ransomware attack.
The cyber criminals have demanded a fee of about United States dollars 300 in crypto-currencies like Bitcoin for unlocking the device.
The "WannaCry" worm global attack, which locks computers and demands a US$300 (S$420) ransom, sowed chaos on Friday through the computer systems of some NHS hospitals which cancelled operations and reduced non-emergency care.
"(There have been) remarkably few payments so far that we've noticed as we are tracking this, so most people are not paying this, so there isn't a lot of money being made by criminal organizations so far", he said. "Nevertheless, one should never pay the ransom as it will encourage attackers", said Kiran Deshpande, Co-founder and President of Mojo Networks.style="text-align: center;"