Ever heard of Stuxnet? If you have a vague interest in how hacking can effect physical things it is well worth reading about. But in short Stuxnet is a "worm" computer virus that effected only a specific model of lab equipment that control centrifuges for separating nuclear material.
When it found out it was connect to one of these centrifuges it would very cleverly cause the physical centrifuge to explode.
Now yes, this is taking it to the extreme. But it it shows how computer hacking can do physical harm, with the potential to harm humans.