Minecraft- civil war?

ok so heres the deal. i had my own private server when some popular kids from my school decided to hack it kick me off as admin and have it for themselves. luckily i know how to mod and they dont so i retaliated and started to grief there stuff as like a guerilla warfare type of thing. luckily the phoney admin dosnt know how to ban. my goal is to push those invaders out. i also got some of my pals from /b/ and /v/ to assist. any advice on tacics and how to cripple them once and for all?