Ensure you have a definition version equal to or later than:
Threat definition version: 1.247.197.0
Version created on: 12:04:25 PM : Tuesday, June 27 2017
Last Update: 12:04:25 PM : Tuesday, June 27 2017

In addition, the free Microsoft Safety Scanner http://www.microsoft.com/security/scanner/ is designed to detect this threat as well as many others.

Those who use antivirus solutions other than Microsoft should check with their support team for security measures.

Recommendations :

Few steps to mitigate against new ransomware:

1. Ensure you have the latest security updates installed.
2. Ensure you have the latest Anti-Virus Signatures from your preferred Anti-Virus vendor.
3. Do not open emails/attachments from unknown/anonymous sources.
4. Use recommended SPAM filtering solutions and custom ports.

Note: These are good security defense-in-depth recommendations that may prevent being infected by this ransomware, but these steps alone do not ensure against infection.

Source Credits: Microsoft