When my son, Ian, was 3, I bought him a cellphone. It had three buttons: "Call Mom," "Call Dad" and "Call Grandma." He was young, but it helped us feel better he could reach us in case of an emergency ...

Coders have a storied tradition of creating back doors in programs (or sometimes just fun little Easter eggs) that can only be accessed with a special "key." This has happened for almost as long as ...