Esta é a mesma pergunta de falha do servidor: Como o CTRL-ALT-DEL para logar torna o Windows mais seguro? .
Aqui está a resposta aceita de lá, por Oskar Duveborn :
The Windows (NT) kernel is designed to reserve the notification of this key combination to a single process: Winlogon. So, as long as the Windows installation itself is working as it should - no third party application can respond to this key combination (if it could, it could present a fake logon window and keylog your password ;)