Tiger is correct, it is not possible to block your IP address on the internet and even if you could, it would not be possible to do anything on the net. You should just get a firewall such as sygate to filter traffic to ensure that you will not be hacked. I prefer sygate over zonealarm because zonealarm is not secure and it screws a lot of stuff up and has uneeded features. The best feature of sygate would be the seath mode browsing, which shows you IP to websites but does not forward browser or os information to sites. I also like the DLL auth feature, this helps you keep track of new dlls to ensure your system files have not been tampered with.

If you have linux, try out iptables, it is the de facto standard for linux based firewalls and, with all linux features, you have complete control over your rule sets.