Forefront antivirus definition not updating
After some searching I found it was an issue with HTTPS and the solution was to disable HTTPS or enable TLS.
You can take the scripts and the first part of this process (the definition download) and use it with any other distribution application you have deployed in your organization. Download Definitions and extract the file to C:\FCSDef (it is possible to extract to a different folder, but this will require a change of path in the scripts). Open C:\FCSDef and Right-Click the Definitions Folder - Sharing.
Even if you have an up-to-date antivirus running on your computer, sometimes these threats are very hard to find and remove, often masquerading as part of the operating system.
For this reason, Microsoft offers Windows Defender Offline, which is a version of its antivirus that you can run from a USB drive to help you remove malicious code that is infecting Windows 10.
Download and own part 1 to 21 of the SCCM Installation Guide in a single PDF file.
The PDF file is a 162 pages document that contains all informations to install and configure SCCM 2012 R2 or SCCM 1511 and later (Current Branch).