how do I update the Microsoft Defender, Antimalware Client Version while offline

For an offline device, the Microsoft Defender Antimalware platform (Antimalware Client Version) can only be updated by using one of the supported update channels and packages; there is no separate “offline-only” platform installer beyond what is documented.

Use these supported options for platform (client) updates:

1. Windows Update / WSUS / SUP (preferred)
   • Platform updates for Microsoft Defender Antivirus are delivered as regular Windows updates.
   • On a managed or isolated network, import the relevant Defender platform update (for example, KB4052623) into WSUS or your Software Update Point (SUP), then deploy it to the offline device.
   • If using WSUS/SUP, ensure the Defender platform update is approved and that the offline device can reach the WSUS/SUP server.
2. Windows Update Catalog (manual, semi‑offline)
   • From a connected machine, go to the Windows Update Catalog entry for the Defender platform update (for example, KB4052623) and download the appropriate package for Windows 10, version 1809.
   • Transfer the downloaded .msu/.cab file to the offline device (USB or other removable media).
   • On the offline device, install the package (for example, by double‑clicking the .msu or using DISM if needed).
   • After installation and a reboot if required, confirm the new platform version.
3. Verify the platform version
   • On the offline device, open an elevated PowerShell window and run:

          Get-MPComputerStatus | Format-Table AMProductVersion
     

   • This shows the installed Antimalware platform (Antimalware Client Version). Compare it with the latest platform version listed in the Microsoft Update Catalog entry (for example, KB4052623) to confirm the update succeeded.
4. Keep security intelligence and engine in sync
   • Platform updates alone are not sufficient; security intelligence and engine updates must also be current.
   • For offline devices, download the latest security intelligence and engine updates from the Microsoft Malware Protection Center on a connected machine and transfer them to the offline device, or configure a file share/UNC source as described in the Defender update management guidance.

If the platform update package fails to install, verify that:

• The package matches Windows 10 version 1809 and the system architecture (x64/x86).
• No other antivirus is registered as primary (which can disable Defender and block updates).

References:

• Microsoft Defender Antivirus security intelligence and product updates and support
• Evaluate Microsoft Defender Antivirus using Microsoft Defender Endpoint Security Settings Management (Endpoint security policies)
• Run and review the results of a Microsoft Defender Offline scan
• Antivirus and antimalware software: FAQ