Source: Windows Central
Although after the installation of Windows 10, the built-in version of Microsoft Defender Antivirus will download and apply the most recent updates automatically, the process does not happen immediately, leaving the system temporarily vulnerable to attacks during this period.
Since it could be many hours before the system receives the update, Microsoft created a tool, which allows system administrators (and technical users) to service an image to maintain an updated version of the anti-malware solution, even before deployment with a few commands reducing exposure.
The solution is available for Windows 10 Home, Pro, and Enterprise as well as for Windows Server 2019 and 2016. It includes the most recent updates (until the release of the standalone package) and a PowerShell script that automates the process to update the installation image (install.wim) or Virtual Hard Disk (VHD) files.