The original author of the code of WannaCry was the NSA. It has been stolen to them and put online since a few months. It has been only slightly modified, and it could have been even done by a non professional. The people needing to be lectured are the ITs of the businesses victims of this virus : a patch was available from Microsoft since March, and any personal computer with auto updates was safe. But some ITs want to control everything, and to control any patch. It is unacceptable when it comes to security patches/updates. If I was the owner of one of these businesses, I would fire them for professional misconduct.
@topffer that is very true, it was something very avoidable in the first place. The patch had always been available, I think even for operating systems that are no longer supported, it's a bitter lesson learned but on the positive it would pave a way to improve security standards and not take things forgranted such as the posibility of a back door exploit and future perceived threats and weaknesses.
@louievill As long as the source code is not available, there is always a possibility of backdoors, and Windows will never be completely safe. If hackers are quite never targeting Unix/Linux, there is a good reason : a virus like this one would be unable to do any damage out of the home directory of an infected computer. When I read that some small businesses paying large amounts of money to maintain their computers/software/networks, have been victim of WannaCry, and that no backup was done, it makes me angry.