I wouldn't rely on McAfee to detect all future variants of this ransomware. You must ensure Automatic Update for Windows is enabled.
This ransomware exploits a vulnerability in Windows. Microsoft patched the vulnerability back in March (MS17-010) and if you had Automatic Updates for Windows enabled, your computer has been protected.
If you don't have Windows Update set to Automatic, set it and update it. If you don't know how to set it, provide your OS and someone will provide instructions.