Stream of new accounts

[mozart101]

I set up a server recently and had no activity and then yesterday I started getting a new account every 2 to 3 mins like a machine was setting them up. They all showed as random IP's in the world.exe window when they connect and random account names. They never make a character but they keep creating accounts. I'm not sure what the goal of it is but I am wondering if anyone else has had this happen on their server.
I locked my server for a day and then unlocked it and almost immediately the accounts started rolling in again every 2-3 mins.

Thanks!