I am not, in general, a proponent of corporal punishment, but in the case of virus writers, I would be willing to make an exception. I think they should chop the fingers off anyone that writes and releases a virus.
Let's see them click their mouses with no fingers!
Ophelia, you have just as much chance of receiving a virus from someone you know as from someone you don't. More, perhaps. A friend is likely to have your e-mail address in their address book. Many viruses distribute themselves by using addresses found in the address book as their next destinations. Your best defense is some good anti-virus software, updated frequently. It will watch your incoming e-mail and quaranteen infected files.