Microsoft Defender for Business Server (Annual Subscription) Microsoft Defender for Business servers is an add-on to Defender for Business. This new offering enables you to secure your server operating systems with the same protection that you get for client devices in Defender for Business. Important In order to add on Microsoft Defender for Business servers, you'll need at least one paid license for Microsoft 365 Business Premium or Defender for Business (standalone). You'll need one Microsoft Defender for Business servers license per server instance, although you don't assign it to any devices or users. There's a limit of 60 Microsoft Defender for Business servers licenses per subscription to Microsoft 365 Business Premium or Defender for Business. Alternately, you could use Microsoft Defender for Servers Plan 1 or Plan 2 to onboard your servers. To learn more, see What happens if I have a mix of Microsoft endpoint security subscriptions? Related Product : Microsoft Defender Collections Microsoft Defender for Office 365 (Annual Subscription) Microsoft Defender for Business (Annual Subscription) Microsoft Defender for Endpoint (Annual Subscription)