A useful tool to help prevent infection from cryptolocker viruses:
It’s Free, simple and easy to use / deploy.
This tool has been known to work. For this to work you need to have 1 file that has not been encrypted and it’s encrypted version. You could use a default OS file such as Windows Sample pictures or the IIS default image. The tool compares the two to work out the decryption key.
This tool is also Free!