NHS cyber attack: Analyst, 22, discovers WannaCry ransomware’s hidden kill switch ‘completely by accident’ | The Independent

A 22-year-old cybersecurity analyst who tweets as “MalwareTech” accidentally halted the spread of the devastating WannaCry ransomware by purchasing a domain name hidden in the program for approximately £8.29 ($10.69). The domain name was written into the software by the ransomeware’s hackers to act as a kill switch: whenever the program tried to infect a computer, it would attempt to contact the webpage. If it was contacted successfully, it would cease the attack; if it failed, it would continue.