Okay. Let's see if I can understand what you're saying.
You shouldn't get a virus if your shared computer isn't on. Hackers and viruses can't get to what's not there, but they can get to your network if it's online. I would guess that viruses can possibly spread across a network of computers.
"I'm not gonna lie to you, Marge... Well, goodbye."
- Homer Simpson, The Simpsons
"Help me, help me, won't you? Sing me, sing me one last song." - Alkaline Trio (Help Me)
"Sometimes the questions are complicated and the answers are simple."
- Theodor Seuss Geisel, a.k.a. Dr. Seuss