Update - 3:30pm: 200,000 victims worldwide have now been hit by the "WannaCry" cyber attack.
Europol says the ransom-ware virus is now affecting users in at least 150 countries.
There are fears some Irish networks may be affected - but there is only one confirmed case so far.
The HSE says it is assisting a healthcare unit in County Wexford that has had files frozen by the virus - however the centre is not connected to the main HSE network.
Update - 11.45am: The head of Europol has confirmed a major cyber attack has targeted 200,000 victims in at least 150 countries.
The Government has been urged to increase funding for cyber security protection in light of the hacking.
Europol director Rob Wainwright said the attack was indiscriminate across the private and public sectors.
"At the moment we are in the face of an escalating threat, the numbers are going up, I am worried about how the numbers will continue to grow when people go to work and turn their machines on Monday morning.
"The latest count is over 200,000 victims in at least 150 countries. Many of those will be businesses including large corporations."
Organisations across the globe, including investigators from the National Crime Agency (NCA), are now working non-stop to hunt down those responsible for the ransomware.
Russia appeared to be the hardest hit nation, with its interior and emergencies ministries and biggest bank, Sberbank, saying they were targeted.
The interior ministry said on its website around 1,000 computers had been infected but it had localised the virus.
Business group IBEC is advising members to take extra vigilance regarding cyber security.
Its head of digital policy, Erik O'Donovan, says: "Safeguarding the resilience of our digital infrastructure and economy is a key priority for business.
Ibec has previously called for adequate resourcing of the National Cyber Security Centre and the implementation of a cyber security programme.
"Government provided extra funding in this regard to the Department of Communications, Climate Action and Environment in Budget 2017 and in view of the increased threat we call for this funding to be increased significantly further.
"Adequate cyber security infrastructure is of critical importance to all companies in Ireland and is a major consideration in securing inward investment.
"The business sector invests heavily in cyber security and it is essential that the Department of Communications, Climate Action and Environment has adequate resources to address the related policy issues including the implementation of the Directive on Security of Network and Information Systems."
Earlier: It is feared more cases of the WANNACRY cyber attack will be uncovered in Ireland as businesses reopen tomorrow.
A small HSE funded healthcare facility in Wexford has been impacted by the ransomware, but it is not connected to the health authority's network.
More than 100 countries and at least 75,000 citizens have been targeted since Friday.
The HSE is working to secure thousands of its devices which could take a number of days.
It has taken a series of actions to reduce the risk of disruption to services, including removing access for incoming communications on the afternoon of the 13th as a way of limiting the exposure to the network.
The HSE said: "Efforts will continue over the weekend and into next week to ensure that services across the public sector remain unaffected and that the private sector receives any support or information required."
The National Cyber Security Centre said they are continuing to actively monitor the situation, and to engage with entities across Government and the private sector in terms of managing the response to this malware.
In a statement the Department of Communications said that "The situation is still evolving, but international contacts are ongoing and more clarity is becoming available on an hourly basis as to how this malware propagates and how it can be dealt with."
They said that "while a number of systems have been targeted, it appears at this point that only one active incident has arisen in Ireland.
"It appears that a small Centre funded by the HSE in Wexford has been affected by the malware behind the present cyber attack," they added that "They are not actually connected to the HSE network & do not pose a broader risk."
Thankfully the threat was isolated and was prevented from spreading.
They said the centre was removed from the incoming email list, and the affected hardware was removed from the system.
They also said that the remaining equipment has also been patched. Finally, they said that The National Cyber Security Centre is also involved, providing assistance and support as required.