Umm, I think I see a basic difference in @geek and @Iszi here. The original C/A/Del sequence was supposed to help keep an Accidental keying of the sequence from happening by being an unlikely combination to be used and then was picked up by everyone else as a secure sequence and may have been worked into the kernel to prevent interception, I'm not knowledgeable enough to comment on that point. However, Like all things on a computer, the individual who owns it can do quite a bit with it that the manufacturer either can't, or, won't, ( for various reasons ) be able to block or prevent. One of the things they most likely would not be able to stop, is for someone to come up with someway to make a simple keystroke or click of the mouse, combine those signals and then pass it by the kernel, thus bypassing the original intention of the security feature. Not saying it should be done ( not by newbies anyway ), just that it could be done.