You can scan instances to see only a report of missing patches, or you can scan and automatically install all missing patches.” The AWS Systems Manager Patch Manager provides patching capabilities for common operating systems, dashboard and reporting functions, and allows for the scheduling of patch cycles.

Does AWS patch EC2?

Patching your Windows EC2 instances using AWS Systems Manager Patch Manager. Patch Manager automates the process of patching Windows and Linux managed instances. Use this feature of AWS Systems Manager to scan your instances for missing patches or scan and install missing patches.

How patches are installed?

Patch Manager, a capability of AWS Systems Manager, uses the appropriate built-in mechanism for an operating system type to install updates on an instance. For example, on Windows Server, the Windows Update API is used, and on Amazon Linux the yum package manager is used.