But a phishing program can just show the enter password screen, without the ctrl alt del prompt. Few users understand the security need to press ctrl alt del. And in newer Windows, it doesn't seem to prompt unless you enable it via GP.
https://i.stack.imgur.com/LHDfV.png
And the user would say "oh, another stupid UAC prompt", enter their password, and that would be that -- UAC doesn't stop and say "press ctrl-alt-delete to enter your password". If it did, then that would significantly decrease the risk here.
Applications cannot fake ctrl+alt+del.
That said you can integrate with the windows login and extend it to show w/e you want I've written a client for a smart card for GINA a long long time ago.
https://msdn.microsoft.com/en-us/library/windows/desktop/ms7...
Ctrl-Alt-Delete on windows is a privileged hotkey that goes directly to the kernel. A phishing program can't intercept it once it has been pressed. If you know that Ctrl-Alt-Delete has been pressed, you are already privileged as the kernel and would be able to compromise a hypothetical protected screen buffer anyways.
https://i.imgur.com/BE0xN3i.png
The Windows login screen here doesn't allow you to type in the password until you press the magical keys that only the kernel can access. This significantly increases security, since any phishing program that puts up a fake static image doesn't know when to present the login dialog.