Wanna Decryptor, also known as WannaCry or wcry, is a specific ransomware program that locks all the data on a computer system and leaves the user with only two files: instructions on what to do next and the Wanna Decryptor program itself.

When the software is opened it tells computer users that their files have been encryted, and gives them a few days to pay up, warning that their files will otherwise be deleted. It demands payment in Bitcoin, gives instructions on how to buy it, and provides a Bitcoin address to send it to.

Most computer security companies have ransomware decryption tools that can bypass the software.

It was used in a major cyber attack that affected organisations across the world including the NHS and Telefonica in Spain.