What was the WannaCry attack and what were its lessons for NHS cybersecurity?

The WannaCry ransomware attack (May 2017) affected 81 NHS organisations in England, causing widespread disruption including cancelled appointments and diverted ambulances. Key lessons included the critical importance of patching and updating systems, replacing legacy infrastructure, network segmentation, business continuity planning, and board-level cybersecurity governance. It demonstrated that cyber attacks on healthcare directly endanger patient safety.