Marcus Hutchins, a 22-year-old who loves pizzas and surfing, managed to halt the global spread of the attack from his parent's home in the south of England.
He stopped the virus in just a few hours - by which point it had brought chaos to thousands including the NHS , banks and government agencies.
And now Marcus has said he is working with the National Cyber Security Centre amid fears the chaos will return when Brits turn on their computers after the weekend.
It is thought he worked from a small bedroom at his parents' home, packed with takeaway pizza boxes
The virus, known as WannaCrypt, targets the thousands of PCs still using old Microsoft systems.
Marcus - who goes by the online moniker MalwareTech - told MailOnline: "I'm not so worried with emails, it's supposedly that this ransomware actually drops a back door and we don't know yet if our fix kills the backdoor as well.
"There is a possibility someone could just re-hack the systems."
"On Monday there is a good risk that there will be another attack so I'm going to try to keep everyone informed."
One of Marcus's friends told The Telegraph that the computer whizzkid was just "doing his job" when he put a halt to the spread of the virus.
Kurtis Baron, founder of Fidus Information Security, added: "He is a really nice friend and also a business colleague.
"It is not a job to him, more a passion that he happens to get paid for."
Marcus realised that by registering a website domain name the virus code could be stopped.
On Sunday, the IT expert himself claimed that hackers from China had tried to hijack the “kill switch” used to prevent the attacks.
He said he had been sent evidence in the form of an email that someone in China had attempted to steal the domain since Friday.
Computer experts have warned the block on the virus may only be temporary and the hackers could easily start up a new one capable of infecting millions more computers within days.
Steven Wilson, Head of Europol’s European Cybercrime Centre, told Sky News it was now important IT departments checked their systems on Monday morning to ensure they had not been compromised.
He added: “It’s not a massively sophisticated attack.
"What is new is the use of a worm to propagate through systems.
“It is beyond anything we have seen before.”
The threat from China and Russia could open up huge implications for the nation’s security prompting Labour’s shadow health secretary, Jon Ashworth, to blame the Tory Government for being “complacent” about the threat.
Challenging Ministers to release their risk assessment to prove they had been taking it seriously, he said: “I would say to the government today, publish the Department of Health’s risk register so we will know how seriously the government were taking a potential cyber attack.”