Table of Contents

Microsoft - Windows - Defender - Antivirus

Microsoft Security Intelligence - Security intelligence updates for Microsoft Defender Antivirus and other Microsoft antimalware

Microsoft Defender - Microsoft Defender Antivirus security intelligence and product updates
Microsoft Defender - Configure and validate Microsoft Defender Antivirus network connections
Microsoft Defender - Manage the sources for Microsoft Defender Antivirus protection updates

Microsoft Defender - Deploy, manage, and report on Microsoft Defender Antivirus
Microsoft Defender - Configure Microsoft Defender Antivirus on a remote desktop or virtual desktop infrastructure environment

Notes

Firewall URLs

Allowing access to the following URLs in the firewall, in addition to the License Activation URLs, and the Windows Update URLs seems to be enough to allow (a heavily outdated) Defender Antivirus to update it's Security Intelligence definition patterns:

crl.microsoft.com
ctldl.windowsupdate.com
definitionupdates.microsoft.com
download.windowsupdate.com
fe3cr.delivery.mp.microsoft.com
go.microsoft.com
www.microsoft.com

Source:Microsoft Defender - Configure and validate Microsoft Defender Antivirus network connections