[entwisi]

actually if you use a router nasties can't get to your computer as it is effectively 'hidden' behind your router. Only ports that you specifiaccly open up and tell your router to send to yor PC can possibly let anything through. When you make a request to teh internet your router does a thing called Network Address translation so that only thngs that you specifically request can come back in and be passed to your PC.

The best way to think of it is as two filds, the internet field and your garden, your router is just a bridge over a river between the two but a special bridge that knows what is and isn't allowed to pass over.