The Ctrl – Alt – Del key sequence that have to press before logging into the computer is called Secure Attention Sequence (SAS) in technical terms. It is not enabled by default in Personal Computers which are not a part of Domain network.
Secure Attention Sequence is a term specific to Microsoft Operating System, Windows and is handled by Winlogon component of the Windows Kernel. The Secure Attention Key is used to make login spoofing impossible because the user has to press those keys before typing in his username and password.
Secure Attention Keys for some of other Operating Systems are as follows:
Ctrl – Alt – Pause for Linux
Control -X Control-R for AID
Break for OpenVMS
Shift – STOP for Plato IV