Make sure its a newer version and up-to-date..if it's an old version becareful and keep it low profile(Im not kidding)
IPB Released an Update, so I suggest you get that and when I say keep it low profile, Im just saying..if it gets really big and tons of people come and try hack it..its not going to be hard. Good Luck -_-
I know a couple things. First thing you can do is upload a mod that makes it so you can't delete admins. Another is make hard passwords and look for scripts or attachments. You can make only root admin have acp access and limited to everyone so their chances are small. Also make a back up every week just incase.