You have 15 Azure virtual machines in a resource group named RG1.

Microsoft Defender for Cloud helps you prevent, detect, and respond to threats. Defender for Cloud gives you increased visibility into, and control over, the security of your Azure resources. It provides integrated security monitoring and policy management across your Azure subscriptions. It helps detect threats that might otherwise go unnoticed, and works with a broad ecosystem of security solutions.

Defender for Cloud helps you optimize and monitor the security of your virtual machines by:

Providing security recommendations for the virtual machines. Example recommendations include: apply system updates, configure ACLs endpoints, enable antimalware, enable network security groups, and apply disk encryption.

Monitoring the state of your virtual machines.

https://learn.microsoft.com/en-us/azure/security/fundamentals/virtual-machines-overview