In May 2017, the infamous Lazarus Group launched a global ransomware attack known as WannaCry, crippling over 80 NHS hospital trusts in the UK. This operation explores the devastating impact on healthcare services, highlighting the vulnerability of unpatched Windows XP systems, the chaos caused by canceled surgeries, and the serendipitous discovery of a kill-switch domain that halted further damage. Participants will delve into the intricacies of the attack, learning to identify and mitigate similar threats in the future.