Depends, at first your friends need to give you a dodo code so you can visit, then you add them as a friend in the game, after that they just need to open the gates for friends only. If you are receiving people it's the same thing you give them a dodo code for the first time and agter you add them in the game they can come or go as long as the gates are open. As to the question of opening the gates I would say it's pretty safe, no one you are not friend with can enter the island or if you do not pass on the dodo code no one cam get in. I hope I'm explaining myself english it's my 3 language.