Over the weekend, a cyber attack the likes of which the world has never seen held important data, pictures, and information hostage demanding Bitcoin ransom payments from anxious users everywhere.
Darien Huss, a senior security research engineer at Proofpoint, warned that "a new attack" was a major concern following the first cyber assault.
Hospitals were forced to turn away patients and cancel appointments.
Foreign minister Julie Bishop on Sunday also confirmed there was one business under investigation of a possible cyber attack.
It has attacked hundreds of thousands of computers, security experts say, from hospital systems in the United Kingdom and a telecom company in Spain to universities and large companies in Asia.
SHANGHAI-"Hundreds of thousands" of Chinese computers at almost 30,000 institutions including government agencies have been hit by the global ransomware attack, a leading Chinese security-software provider has said, though the Asian impact has otherwise been relatively muted.
Large swathes of the NHS have been paralysed by the cyber attack, which hit 200,000 victims in 150 countries around the world.More news: Roger Ailes, former Fox News chairman, dead at 77
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"Systems are returning to normal today and I would like to thank NHS staff for their hard work over the weekend".
In a statement, NHS Digital said that IT staff across the NHS were sent a link to the latest Windows XP patch at the end of April. In the case of this ransomware attack, Microsoft released a patch weeks before the attack hit, which would have protected systems by not permitting the ransomware to take hold.
The National Crime Agency has said it will "take time" to investigate who is behind the attacks, but said it has started "identifying patterns" in the swathes of data it has access to.
Attackers target users via an email phishing scam, according to the U.S. Computer Emergency Readiness Team.
Oxford University Hospitals NHS Foundation Trust said it has not been affected by the attack but Oxford University Hospitals NHS Foundation Trust communications manager Roy Probert said the trust is still remaining vigilant. The cyberattackers demanded payments of $300 or more from users to unlock their devices.
The US security firm Symantec said the attack appeared to be indiscriminate.
Petients have been told they can attend their GP surgeries as normal following last week's computer cyber attack - though some facilities were still seeing difficulties on Monday.