A custom system with millions of lines of code controlling a multimillion dollar theme park can be operated by a 13 year old who has seen a Unix system before. Knowing an operating system means you know how to run any application on that system, even custom apps. You cannot stop a destructive program or virus by unplugging the computer. Presumably the virus has it's own built-in power supply. You cannot stop a destructive program downloading onto your system by unplugging the phone line.
Computers only crash if a virus or a hacker is involved.