"As cybercriminals become more sophisticated, there is simply no way for customers to protect themselves against threats unless they update their systems", Mr Smith said.
More than 75,000 similar attacks reportedly happened in nearly 100 countries, with Russia, Ukraine and Taiwan hardest hit, according to the cybersecurity firm Avast. New versions of the worm are expected, the experts said, and the extent - and economic cost - of the damage from Friday's attack were unclear.
Fortunately, a 22-year-old British researcher and 20-something American security engineer discovered a "kill switch" and unregistered domain that halted the attack, reports the Associated Press.
"If you have a scheduled appointment you are advised to attend as normal unless you are told otherwise". Companies across the company are expected to be running checks and updating software today.
Europol executive director Rob Wainwright had warned on Sunday the situation could worsen when workers return to their offices on Monday after the weekend and logged on.
"It seems inconceivable that organisations such as the NHS are prepared to jeopardise highly confidential patient data or critical infrastructure through inadequate cyber security that relies heavily on out-dated anti-virus technologies, when effective alternatives like file-regeneration are available".
Pressure mounts on Trump as Comey agrees to testify
In that same conversation, Trump referred to Comey as "crazy" and "a real nut job", according to the Times . Legal experts said the ethics rule can be waived by the Justice Department, which appointed Mueller.
Frenchmen claim cure for WannaCry-infected computers
On Thursday, French computer-security researcher Adrien Guinet found a way to unscramble the files without paying the $300 ransom. Cyber-attacks on the scale of WannaCry may remind organisations about the need to maintain their IT security.
Trump tells Russians Comey was a 'nut job'
Robert Mueller, who served as FBI chief under George W Bush, was appointed this week as special counsel for the investigation. A memo by fired FBI Director Comey alleged Trump even asked that the probe into Flynn be shut down.
South Korea wants to reopen communications with the North
The North defends its weapons programs as necessary to counter USA hostility and regularly threatens to destroy the United States. Relations between Beijing and Seoul, strained by disagreement over South Korea's hosting of the U.S.