20,000 NHS computers in Wales are in danger of being hacked into, Plaid Cymru claimed last week.
The Principality's nationalist party said the service continues to rely too heavily on 15-year-old Windows XP software which Microsoft stopped supporting over a year ago.
The party claims it's been warned by IT security experts that hackers could potentially access confidential information when machines running XP are connected to the Internet.
The party's health spokesperson Elin Jones said the situation reflected "a wider lethargy in utilising modern technology" in the service,
NHS Wales responded quickly, saying there was "a very clear programme" to replace Windows software and claiming the numbers of XP devices is inaccurate.
Its National Infrastructure Management Board put out a statement that said, "NHS Wales takes IT security very seriously and operating systems are one of several layers of security utilised.
"There is a very clear programme to replace Windows XP and we have prioritised the replacement of any devices that could impact patient care, implementing modern technology.
"The number of devices running Windows XP is reducing daily, and the figures in the article are already now significantly outdated due to the work conducted both locally and nationally.
"There is no record of any technology not being implemented or delayed due to the presence of Windows XP."
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