Windows NT is designed so that, unless security is already compromised in some other way, only the WinLogon process, a trusted system process, can receive notification of this keystroke combination. This is because the kernel
remembers the Process ID
of the WinLogon process, and allows only that process to receive the notification. This keystroke combination is thus called the Secure Attention Sequence
. A user pressing Control-Alt-Delete can be sure that it is the operating system (specifically the WinLogon process), rather than a third party program, that is responding to the key combination, and that it is therefore safe to enter a password. It was chosen as the secure attention key in Windows (instead of, for example, the System Request
key), because on the PC platform no program could reasonably expect to redefine this keystroke combination for its own purposes.