Your IP address is available to all and sundry. The IP addy means that pages you 'go to' on the net are delivered to your computer. You do not visit sites, they 'visit' you so you need an IP address so they know where to go. For home users their IP address is different each time they connect (dynamic). Many businesses or if you are running a server have static IP addresses, i.e the address is always the same so that outside users can connect each time.
Get an up to date AV and MS Antispy and you will have no chance of being 'hacked' on a home computer...even if you did not have these and went on the net commando, you would still have no chance of being hacked...viruses and trojan maybe.