How to set up multi-factor authentication (MFA) for Veeam Agent for Windows

A Veeam Agent backup job targeted at the Microsoft OneDrive cloud storage fails with the following warning: "Due to a configuration change made by your administrator, or because you moved to a new location, you must use multi-factor authentication to access"

The warning is caused by multi-factor authentication (MFA) enforced for Microsoft OneDrive.
Microsoft OneDrive requires Veeam Agent for Windows to authenticate using the Microsoft Authetificator app.

To continue working with the Microsoft OneDrive cloud storage, you need to re-authenticate with the MFA authentication method.

1. Open backup job settings.
2. Go to the Microsoft OneDrive step of the wizard.
3. Re-connect to Microsoft OneDrive as described in the Microsoft OneDrive Settings section of the Veeam Agent for Microsoft Windows User Guide.
4. Sign in using the multi-factor authentication. For more details about the Microsoft Authetificator app, see Microsoft documentation.

Microsoft replaced Baseline Policies with Security Defaults on February 29th, 2020. Enforcing MFA across partner users is one of the changes. For more details, see Partner Security Requirements.