Seriously, it gets annoying to see these kinds of topics. If you hosted that build on Internet, it would be free for the taking. If it's a very popular server then you see you kind of have a protection thing here, for example Pecon7's Boss Battles, if anybody copies that server and tries to host it, lots of people will drama it in defense for Pecon7. But if it's the host trying to drama the person who did it, then that's not good.
Some people may just want to save your build to look at it, and study the style. That's not bad at all, they are learning from you and you should be honored. People who host builds with your build stolen are idiots yes, but I will say it again: you hosted that server in public, the build is free for the taking. If you don't want your build getting stolen, host it in Singleplayer or in a passworded server with some friends.
Also, please, please do not try to modify the save system. No matter how much you don't want a person to steal your build, please don't modify it. It will forget up the game and Badspot will be pissed. Badspot even made a post about how he doesn't want it forgeted up, I can't find it at this time but if anybody could find it and post it here, that would be great. Thank you for your time.