It is not a hardware interrupt in the sense that there's nothing special about this key combination to generate a specific interrupt. The only related interrupts are the keyboard interrupts that happen for every keyboard activity, which the BIOS interprets and takes actions like turning on a key LED and storing the actions in a memory buffer (this is all in "real mode" on x86 processors) before that goes further up to the application. Capturing the keyboard interrupt could allow one to intercept specific keystrokes (like Ctrl+Alt+Del) before the OS gets it, but that's not possible in the OSes the most people use today (which all run in "protected mode").