Virii were mostly spread over floppy (boot block or trojan) back then. While I agree that it's very unlikely that this system will get infected, don't think that times were better back then :)

http://www.teyko.com/View.aspx?id=346&name=Saddam+Virus

...which was a rather brilliant little thing, but a personal hatred as it messed up many a .s files (.s stood for "source code" or "Seka", I guess).