IP Blocker allows you to block accesses to your store, based on the IPv4 address of the access. Once you've copied the plugin's files to your store, use your Zen Cart admin's Tools->IP Blocker to specify the list of addresses. There are two blocks of IP addresses that you specify:
Refer to the plugin's readme.html file (available by clicing the Readme icon below) for more information.
If I've helped you on the Zen Cart forums or you've found one of my free plugins helpful, feel free to give a little back by clicking here.