Microsoft Defender SmartScreen

SmartScreen is Windows' reputation check for downloaded software. When a user runs an installer Windows doesn't recognize, they get the full-screen blue warning: "Windows protected your PC - Microsoft Defender SmartScreen prevented an unrecognized app from starting", with the Run button hidden behind a "More info" link most users never click.

Reputation is earned two ways: through a trusted code signature, or slowly, through enough users running the file anyway. Unsigned installers show "Publisher: Unknown" and start from zero reputation on every release, because each new file hash starts over.

The modern fix is signing through a route SmartScreen trusts. Microsoft's own Azure Trusted Signing gives signed installers established reputation without the old dance of buying EV certificates on USB tokens. Deskifier signs every Windows build this way, so users see the app's real name and publisher instead of the wall.