Originally posted by Latcady:

If you're worried about someone new being a possible troll, one thing to do when you're first allowing a new person into your world is to make a copy of your world file BEFORE you let them log in and just save it in a folder - that way if they're good, awesome no need to do anything else! But if they do suddenly start messing things up, you can get rid of them and restore your old save.

Not 100% perfect but it will mean you won't lose EVERYTHING, just what was done after this troll joined you.

Can you provide some instructions on how to do this? Great idea!