The threat to Northern Ireland from the cyber attack that crippled NHS computer systems in England and Scotland isn't over, police have warned.
The PSNI's cyber crime chief said some systems may already be infected and waiting to activate as staff return to work this morning.
Detective Chief Inspector Douglas Grant said: "While no incidents have been reported in Northern Ireland as yet, we do expect further infections to come to light globally over the next week - and we cannot rule out the possibility that local systems may be vulnerable.
"As people return to work after the weekend, many will have unopened, potentially infected emails in their inboxes, or their systems may already be infected and are waiting to activate.
"It is of the utmost importance that individuals and organisations act to ensure the integrity of our local cyber networks and take appropriate action to reduce the threat posed by cyber criminals."
DCI Grant called on the public, private and voluntary sectors here to take immediate steps to protect their computer systems and reduce their vulnerability.
"We would also recommend that businesses and industries join the local Cyber Information Sharing Partnership (CISP) so they can receive the most up-to-date threat and mitigation information to help protect their cyber security," he said.
Ciaran Martin, chief executive of the UK's National Cyber Security Centre (NCSC), warned there could be a fresh wave of victims today. "We have not yet seen Friday's attack recur, there's been no new wave of attacks," he said.
More than 200,000 computer systems in nearly 100 countries have been infected with the so-called WannaCry ransomware since Friday, causing severe disruption to health services, industry, transport, academia and law enforcement across the globe.
A number of hospitals in England and Scotland were forced to cancel procedures after dozens of NHS systems were brought down. Medical staff reported seeing computers go down "one by one" as the attack took hold, locking machines and demanding money to release the data.
Around a fifth of trusts were hit, amid concerns networks were left vulnerable because they were still using outdated Windows XP software.
In the Republic, the Health Service Executive (HSE) cut its network off from external communications as a precaution. The decision means its facilities will be unable to receive emails from outside the organisation. But HSE chief information officer Richard Corbridge said the impact on patients is unlikely to be significant because email is rarely used to communicate with them.
Any organisations that believe they may be victims of cyber-attack are urged to contact the PSNI immediately on 101 or via the Cyber Crime Reporting Portal on the PSNI website.
The PSNI said the latest advice and patches are now available to protect current and older legacy systems via: https://www.ncsc.gov.uk/guidance/ransomware-latest-ncsc-guidance
The PSNI’S Cyber Crime Centre has issued advice to people concerned about the ransomware threat:
The police also recommend that businesses and industries join the local Cyber Information Sharing Partnership (CISP) for the most up-to-date information.
Victims should contact the police immediately on 101 or via the Cyber Crime reporting portal on the PSNI website, or alternatively through Action Fraud, tel: 0300 1232040.