Unfortunately you really can't on your own and ISP charge lots of money to protect you with one of their firewalls. You really need to protect you IP which means you use VPN software when you connect to anything that you are concern if they obtain your IP. Whatever you do never give person you do not trust your skype id. Skype will tell them your IP even if it changes the second you connect to the skype network.
This is like asking how you stop the idiot from calling you over and over and hanging up. Unless you get someone in power to help you there is nothing you can do.