(This is assuming you have a router, which with that equipment, I'd say you do.)
Do you have access to the router? If so, you could always set up an access restriction or ACL that blocks any sort of internet traffic. If you need help with this, we'll need to know what sort of router you have, though most are easy to configure. However, if you're only connected with a hub or a lower layer device, that kind of rends this post useless and I apologize for wasting your time.
