NHS hack: Hospitals were sent patch that would have prevented chaotic cyber attack

NHS computers have been taken over by hackers at dozens of UK hospitals (Getty Images)

One small mistake might have allowed the hack that brought chaos to the NHS.

Health trusts across England were sent details of a patch that would have kept them safe from the ransomware used in the huge cyber attack, according to NHS Digital.

The attack brought problems for huge swathes of the NHS, leaving almost 50 trusts without proper access to their computers. The problems led to appointments being cancelled, doctors unable to work and may even have caused deaths within affected hospitals.

If computers had been updated in accordance with NHS Digital's advice, hospitals would have been safe from the problems.

The health service has been rebuked for using the outdated Windows XP operating system to store digital information, despite security updates for the software having been discontinued by Microsoft.

The attack has left 47 NHS organisations affected with malware in their system, ranging from hospital trusts to commissioning support units.

Seven hospital trusts are still experiencing serious problems, among them St Bartholomew's Hospital in London, York Teaching Hospital NHS Trust and the University Hospitals of North Midlands Trust.

But NHS Digital said it had made health trusts aware last month of IT protection that could have prevented the attack.

It said in a statement: "NHS Digital issued a targeted update on a secure portal accessible to NHS staff on April 25, and then via a bulletin to more than 10,000 security and IT professionals on April 27 to alert them to this specific issue.

"These alerts included a patch to protect their systems. This guidance was also reissued on Friday following emergence of this issue."

Additional reporting by Press Association