Windows Defender SmartScreen Reports Backup Agent As Unrecognized App
Situation
Windows Defender SmartScreen reports the following warning: Mircosoft Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk
Along with Windows Defender, any other anti-virus software could react similarly
Cause
This is expected behavior from Windows Defender SmartScreen®. Backup Agent version comes with a new MSPBytes code signing certificate which requires gaining a reputation. Windows Defender SmartScreen is equipped with the Application Reputation algorithm. The goal of the Application Reputation experience is to warn users, when appropriate, that a downloaded application has not yet established a reputation.
Read more about on how the Windows Defender SmartScreen works in the How Microsoft Defender SmartScreen works when a user tries to run an app paragraph at docs.microsoft.com
Thus, this warning by Windows Defender SmartScreen is temporary and will disappear in a short time.
Solution
Just go on with the installation: click Run Anyway.