If you have logged on to Windows 10/8/7/Vista, you can use Ctrl+Alt+Del to start Windows Security.
You can refer to this post to enable it: Enable Press Ctrl+Alt+Del Secure Logon On Windows 7 or Vista. However, this feature is disabled by default. This is called a secure attention protection/sequence. If you are still using these Windows operating systems like Windows XP, Windows Vista, and Windows 7, you can use the Ctrl+Alt+Del command to log in to a Windows user account. That is why you need to reboot your computer properly. Although the page cache is flushed and the volumes are safely unmounted, it is quite possible that the running programs are not closed cleanly and your works/documents are not saved properly.
