Large swathes of the NHS were paralysed by the cyber attack, which hit 200,000 victims in 150 countries around the world.
A United Kingdom security researcher known as "MalwareTech", who helped to limit the ransomware attack, predicted "another one coming. quite likely on Monday".
The computer malware had hit 150 countries by the end of Friday.
The attack involves a malware, known as "ransomware", which locks computers and holds users' files for $300 ransom in bitcoin to retrieve files.
The Nissan vehicle plant in Sunderland is still suffering from issues caused by the ransomware attack which forced auto production to a halt on Friday night. Previous year a number of U.S. hospitals had to allegedly pay ransom to get rid of such attacks, though the matter was kept under wraps as the hospitals did not want bad name.
The full scale of the global cyber attack that continues to disrupt the NHS may only become apparent when people return to work on Monday, experts have warned.
Experts say another attack could be imminent and have warned people to ensure their security is up to date. "That's not to say that the attacks are new - it's a repercussion of what happened on Friday".
"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.
John Clark, professor of computer and information security at the University of Sheffield, said the attack should act as a wake-up call for the health service and for businesses and individuals to defend themselves adequately against so-called "ransomware".
According to the reports, in England 48 National Health Service (NHS) trusts reported problems at hospitals, GP surgeries or pharmacies, and 13 NHS organisations in Scotland were also affected.
Dreyfus said everyone that uses a laptop has to make sure that system is fully patched.
"It is thanks to the dedication and hard work of many staff, who worked unstintingly throughout the weekend, came in early this morning and are staying late tonight that we have minimised the effect on patient care".
Friday's attack escalated via combined ransomware techniques with code that spread through recently uncovered weaknesses in Microsoft (MSFT) Windows and, although Microsoft had repaired the vulnerability, computers worldwide had not been patched and fell victim to the hackers.
The Seattle-based tech giant issued guidance for people to protect their systems, while taking the highly unusual step of reissuing security patches first made available in March for Windows XP and other older versions of its operating system.
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