NHS Borders is among more than 30 UK health boards being targeted by cyber attacks.
Staff at the trust face a weekend of disruption as it deals with a computer virus activated yesterday by hackers seeking ransom payouts.
A spokesperson for the trust said: “We can confirm that NHS Borders has been affected by the current national cyber attack, and all necessary control measures have been taken to minimise the impact.”
Three of the trust’s community sites, including smaller hospitals at Peebles, Kelso, Hawick and Duns, are affected, but it declined to clarify which ones have been targeted or confirm that the Borders General Hospital at Melrose is unaffected.
It did insist, however, that patients are not being put at risk by the ransomware attacks and that there appears to be no urgent danger of the confidentiality of their records being compromised.
“The networks at the three affected community sites have been isolated, software has been shut down, and there is no immediate risk to patient care or confidentiality,” it said.
“All other NHS Borders services are currently operating as normal.”
Almost a dozen Scottish health boards have been hit by the hackers locking computers and demanding money to release the data on them.
The National Cyber Security Centre says teams are working round the clock in response to the attack, reported to have hit almost 100 countries, including the US and Russia.
UK Prime Minister Theresa May said the Government is not aware of any evidence that patient records have been compromised.
“This is not targeted at the NHS. It’s an international attack, and a number of countries and organisations have been affected,” she added.
Experts say the virus, called Wanna Decryptor, exploits a vulnerability in Microsoft Windows software first identified by spies at the US National Security Agency (NSA).
The tools were leaked on the web earlier this year after hackers dumped a cache of NSA files following a security breach.
Prior to the dump, Microsoft released a fix, or patch, for the issue, although computers that did not install the update, or could not due to the age of their software, would have been left vulnerable.
The US Department of Homeland Security said on Friday that the patch, released by Microsoft on March 16, “addresses this specific vulnerability, and installing this patch will help secure your systems from the threat”.
In December, it was reported nearly all NHS trusts were using an obsolete version of Windows that Microsoft had stopped providing security updates for in April 2014.
Data acquired by software firm Citrix under freedom of information laws suggested 90% of trusts were using Windows XP, then a 15-year-old system.
It is not known how many computers across the NHS today are still using Windows XP or recent variants Windows 8 and Windows 10 or whether NHS Borders is among them.