In May 2017, a piece of ransomware called spread around the world. It lasted four days and affected over 200,000 computers in 150 countries. Only about $130,000 (USD) was ever paid in ransom, but the attack affected a lot of large companies and organizations. The United Kingdom's National Health Service (NHS) was hit hard by WannaCry. Hospitals could not access their files, and so many surgeries were cancelled and patients had to be turned away. The NHS was especially at risk because it was using a version of the Windows operating system called Windows XP that Microsoft no longer supported. This meant that Microsoft had not been sending out security updates for this version of Windows, leaving it open to the WannaCry virus. Other systems were affected even though they were running newer versions of Windows, because their users had not yet installed the most recent security updates. Even though it was not designed to actually damage computers or their files, WannaCry led to a lot of wasted time and money, showing how vulnerable the world still is to ransomware attacks.