Microsoft said the WannaCry ransomware attack happened because America's National Security Agency (NSA) stores cyber-weapons. Ransomware is software that blocks computers until the owner pays money to hackers. The NSA helps to stop cyber-attacks. Microsoft said the WannaCry hackers used spying tools from the NSA.

Microsoft said we must wake up to the problem of keeping cyber-weapons. They are as dangerous as missiles. Europe's police said WannaCry hit 200,000 computers in 150 countries. It made many problems for hospitals in Britain. Microsoft told people to back up their files. It said more attacks could come.