Microsoft has announced support for Windows Defender Advanced Threat Protection, a Windows 10 only feature, to Windows 7 SP1 and Windows 8.1. This is to help organizations protect themselves during the transition to Windows 10 from the aforementioned OSs.
https://www.notebookcheck.net/Windows-Defender-ATP-coming-to-Windows-7-and-Windows-8-1.282718.0.html