I have Windows 7 installed in Boot Camp on my 2011 MacBook Pro.
I have configured Windows to require a Ctrl+Alt+Del to log in. This is supposed to prevent malware from putting up a fake login screen.
The MacBook Pro does not have a "Del" key. Well, it does have a "delete" key, but that is equivalent to the "Backspace" key on a Windows keyboard. The MacBook Pro does not have a key equivalent to the "Del" key on a Windows keyboard. You have to press Fn+Delete on the MacBook Pro in order to simulate the Windows "Del" key.
When I press Ctrl+Alt+Fn+Delete on the Windows login screen, it works as it should. But I noticed that Ctrl+Alt+Delete works too, which really means that Ctrl+Alt+Backspace is working. That should not work (I tried it on another Windows PC with a Windows keyboard, and it does not work), and it makes me wonder if it might be a possible security hazard.